


A Pile of Bad Things

by maeinfin



Category: Doctor Who, Doctor Who & Related Fandoms, Doctor Who (2005)
Genre: Alternate Universe - High School, Alternate Universe - Human, Dubious Consent, F/M, First Time, Fluff and Humor, Kissing, Mutual Pining, Older Woman/Younger Man, Oral Sex, Slow Burn, Teacher-Student Relationship
Language: English
Status: In-Progress
Published: 2020-10-05
Updated: 2021-03-04
Packaged: 2021-03-08 04:07:55
Rating: Explicit
Warnings: Underage
Chapters: 11
Words: 31,065
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26839465
Author URL: https://archiveofourown.org/users/maeinfin/pseuds/maeinfin
Summary: U.N.I.T. wasn't the Doctor’s first choice of school to teach at... but when the Brigadier needs help dealing with hell-raising final year student Koschei Oakdown, she couldn't refuse. Even though she really should have.aka, there is no universe where the Master isn't trying to get the Doctor's attention and a little age gap isn't going to stop him.
Relationships: The Doctor/The Master (Doctor Who), Thirteenth Doctor/The Master (Dhawan)
Comments: 111
Kudos: 77





	1. Chapter 1

**Author's Note:**

> This is an underage student/teacher AU and the Master is 17... The Doctor can be any age you imagine.

The Unparalleled National Institute of Technology wasn't Doctor Theta S. Lungbarrow’s first choice of school to teach at. It wasn’t even her last choice; it simply wouldn't have made her list at all, if it weren’t for her old friend and U.N.I.T.’s headmaster, the Brigadier Lethbridge-Stewart.

The Doctor preferred to go to schools where students most needed her help and U.N.I.T. was the very opposite of such a place. Closely linked to both the government and the military, it was a hothouse for the brightest young minds in the country... as long as their parents could afford the extortionate fees, and had the connections to secure the admission in the first place.

It was the type of secondary school that didn’t need the Doctor, and yet here she was, moving into a cosy flat on the school grounds because she hadn’t been able to refuse the Brigadier’s hundredth phone call.

The job itself was simple - teach A-Level Chemistry and Physics to the Year 13 cohort at U.N.I.T. for a year. It was a suspiciously light workload that would only amount to eight teaching hours a week, for which she’d still be earning a full-time salary.

“I’m not being funny, Brig, but something’s not adding up here,” she’d said to the Brigadier who huffed down the phone in reply.

“Nothing gets past you, Doctor,” he said, “We’ve got a situation here at U.N.I.T. and if there’s one person who can find a way out, it’s you.”

It turned out that after a long and celebrated career, the Brigadier was finally ready to retire. The problem was that the school governors wouldn’t accept his resignation unless the ‘situation’ with young Master Oakdown was ‘appropriately handled’ first.

“He can’t be that bad,” the Doctor said, “He’s just a kid!”

“He’s 17 years old,” the Brigadier paused “And you should read a newspaper once in a while.”

He’d hung up, issuing her with a strict command to call him back as soon she’d caught up with the headlines. Thirty minutes later, the Doctor was severely regretting the fact she’d already agreed to take the job. She considered herself the type of person who’d never refuse to help a friend in need, but that was before she’d typed ‘son of Lord Oakdown’ into the internet.

While the Doctor had a passing awareness of Lord and Lady Oakdown, who were often lauded for their political achievements in and around Gallifrey, she’d paid little attention to their wayward son. However, it only took a quick browse through the tabloid websites to get up to speed; it seemed that the young Master was not quite the Oakdown heir that his parents wanted him to be.

According to a questionable profile in The Gallifreyan Weekly on ‘Society’s Almost-Eligible Lords-to-Be’, the young Master had once hacked his way through the neighbouring nation of Traken’s security systems and transferred the entire country’s financial reserves from the Bank of Tremas into his own account in Gallifrey. He’d been ten years old at the time.

After that, his trail of carnage had only intensified. When he was thirteen, he’d taken off with a classmate called Lucy - who by all accounts had been a model student until she’d met the young Oakdown. They’d gone missing for a year and it later emerged that they’d somehow infiltrated the Valiant battleship and had been living there in secret. When they’d gotten bored, they’d set the entire warship on fire and danced around the flames, live-streaming the destruction all over the internet. It’d been a miracle no-one had died and yet, Master Oakdown hadn’t stopped there.

Soon, he’d been thrown out of every respectable boarding school east of the Alpha Centauri coastline. It wasn't long before he’d disappeared again, aged fifteen only to resurface months later at Gallifrey’s hallowed Immortality Gate. Despite the grandiose name, it was only a historical monument with some long-forgotten religious significance. No-one visited except tourists from the Naismith region, whose people still practised the old ways.

That is, until the young Master had shown up with some sort of electrical contraption he’d built himself, convinced he could bring ancient Gallifreyans ‘from the afterlife through the gate’. He’d disappeared from public eye soon after and the gossip rags had speculated that the Gallifreyan High Council had helped his parents secure their son in a hospital abroad.

Clearly, those rumours had been unfounded. On the front page of last week’s edition of The New New Earther, was a smirking photograph of Master Oakdown, freshly bailed out from St Luke's Juvenile Detention Center. At this point, the Doctor was frantically ringing the Brigadier back. While she prided herself on her ability to win round even the most reluctant of students, whatever the ‘situation’ was with Master Oakdown, it was unlikely to be a case of too much backchat and long-overdue homework assignments.

And she was right. Koschei Oakdown had briefly been treated at Gallifrey’s very best hospital and it had worked. He’d calmed down considerably and had spent the intervening two years at U.N.I.T., explained the Brigadier. Even more surprisingly, Miss Oakdown, as she’d preferred to be called, had even decided ‘to turn good’, comparatively speaking. There’d been the odd, deliberate explosion in the science labs and she’d still taken far too much joy in provoking Nardole, the school caretaker but other than that, Miss Oakdown had said she wanted to change and for a time, she’d been doing well.

And then, it’d all gone pear-shaped, the Brigadier lamented.

“Pears have the worst shapes too. I’ve always thought so,” the Doctor said, transfixed by the photo before her. Dressed in old-fashioned Victorian clothing, Miss Oakdown had a startlingly penetrating gaze, even from the computer screen.

“All her progress disappeared in a flash,” the Brigadier continued, “It's as if she’s become a different person. And I don’t mean the identity change.”

Only a few months ago, Miss Oakdown had gone home to her father’s estate for the Easter school holidays. Her parents had been away working and she’d been left to her own devices which was fairly customary for U.N.I.T. students whose families moved in the upper echelons of Gallifreyan society. What was different this time, was how changed Master Oakdown was on his - and it was his again, clarified the Brigadier - return to the school.

He'd come back from Gallifrey City in a near-constant fit of rage, terrorising the younger students incessantly and threatening to throw them off the roof of the French department if they didn’t obey him. And then, on the last day of Year 12, he’d razed the Social Sciences block to the ground. The Brigadier would’ve expelled him instantly if Lord Oakdown didn’t literally hold the purse strings to U.N.I.T.

“Now, there's just two things I want from you, Doctor,” the Brigadier thundered down the line, “I want an effective way of controlling Koschei Oakdown and the safe return of U.N.I.T.’s bank accounts. And after all that, I'll be able to have my retirement party.”

So there she was, reluctantly employed as the school’s newest science teacher and for the first time in her life, the Doctor was dreading the beginning of the school year. She simply couldn’t shake the feeling that whatever happened, it was going to be complete and utter chaos.


	2. Chapter 2

**Notes for the Chapter:**

> Thank you for the lovely encouragement! It fuelled me to give the whole concept a bit more of a poke... I have no plot and no plan but thought I'd try writing another scene and see where it takes me...

It turned out that Koschei Oakdown wasn’t exactly the nightmare student that the Doctor had been expecting. She’d woken up on her first teaching day at U.N.I.T. with the sensation of dread burning in her stomach and by the time she’d reached her classroom, the one thing she was sure of was that she really didn’t want to be there. She’d have run away from Gallifrey entirely if she could.

The problem was, she had no choice but to stay, seeing she’d already promised to help the Brigadier and it wouldn’t be fair to quit a teaching position on the first day of the school year, no matter how bad the young Master Oakdown’s reputation might be. And then, after all that worrying and ruminating, the Doctor’s first A Level Chemistry lesson at the school went perfectly smoothly. In fact, absolutely nothing unexpected or chaotic happened at all, because -

“He wasn’t there,” she said as she shovelled spoonfuls of blue peach crumble into her mouth.

The Brigadier didn’t reply, instead eyeing the colourful assortment of food on the table between them. It was lunch time and the school refectory was packed with staff and students eating carefully prepared, nutritiously balanced meals... except for the Doctor who had skipped directly to four different kinds of dessert.

“You are aware that U.N.I.T. employs one of the finest chefs in Gallifrey?” the Brigadier said eventually, “Alphonse has been awarded three White Point Stars every year since we nabbed him from Darillium.”

“I can tell. This custard is excellent,” the Doctor said, pouring another jugful into her bowl.

“At least get some vegetable pills from the food machine later,” the Brigadier sighed, cutting primly into his kronkburger, “You’re only human, Doctor, you can’t live off sugar alone.”

“Will do,” she hummed cheerily with no intention of doing so, “But you didn’t answer me. What about our missing Master?”

“Are you quite sure that Master Oakdown wasn’t there?” he said carefully.

“Yes!” she said indignantly, “I looked at every single face.”

She would’ve recognised him instantly, she was sure of it. After all, she’d spent the past two weeks combing the internet for every scrap of information she could find about Koschei Oakdown, and now it felt like the image of his glinting eyes was etched into her brain.

“You didn’t see any young men with his hair colour and complexion in your classroom this morning?” the Brigadier pushed.

She chewed slowly, “Yes, but none of them were him.”

“I see,” said the Brigadier, “Well, as you know, we are the Unparalleled-”

“National Institute of Technology. Yes, I do know that, Brig,” the Doctor rolled her eyes, “But what do you do about kids bunking off?”

“-And we have the most advanced, integrated education system this side of Alpha Centauri,” continued the Brigadier, as if she hadn’t spoken, “So if Master Oakdown had missed your class, the bio-scanners would’ve flagged his absence and word would’ve reached me at once.”

“So you’re not worried, because your computers say he came to class. Even though I’m telling you I didn’t see him,” She slurped slowly on a spoonful of custard, wondering if she should tell the Brigadier he was an idiot now or wait until there were fewer students around, but before she could decide either way, he’d pushed his lunch tray aside.

“Time for me to patrol the school grounds,” the Brigadier said, clapping a hand on her shoulder as he left, “Good luck with your first Physics class this afternoon, Doctor. It sounds like you’ll be needing it.”

*********************************************

The U.N.I.T. students were unnervingly silent. It was like standing in front of a classroom of little soldiers, from the way they sat with their spines ramrod straight, to how carefully their eyes tracked the Doctor’s every move as she paced before them.

That morning, she’d been so on edge about Master Oakdown not being there that she’d barely paid any attention to the ones who had shown up. Instead, she'd rattled through the first term’s homework requirements at top speed and then spent the rest of the hour setting fire to a random mixture of chemicals from behind a safety screen. It’d been very dramatic and the students had made all the impressed noises she liked to hear, but in hindsight, it probably hadn’t been the best way to start the school year.

At least half of that morning’s Chemistry students were also taking A Level Physics and they’d clearly told the others about her over lunch. All thirty of them were now watching her with a mixture of skepticism and interest. Either they didn’t think she was capable of getting them through their exams or they weren’t entirely sure who she even was.

To be fair, she couldn’t remember now if she’d even introduced herself that morning, and she certainly hadn’t bothered to ask any of them their names either. On the bright side, that was easy enough to fix.

“I’m the Doctor,” she said, grinning broadly, “You can call me Doctor.”

“Yes, Doctor Lungbarrow,” Thirty voices droned back at her.

She frowned, “That’s not what I said.”

Thirty faces stared at her blankly. She stared back, squashing down the urge to run away again. Normally, the students she taught were far more interesting than this. Even if they didn’t want to learn, they at least had personalities. But that was the problem with the upper echelons of Gallifrey and it wasn't the students' fault they were born into boring households, the Doctor reminded herself.

“Okay, let’s start at the beginning. Why physics?” She pointed at a confident-looking boy sitting in the middle row.

“It’s a good foundation,” he sat up straighter as the Doctor nodded at him eagerly, “For a strong university application.”

“No,” she gasped, horrified, “I mean, yes but no. Someone else say something better!”

“It helps you understand the world,” said a solemn-faced girl by the window.

The Doctor whirled towards her in relief, “And then?”

“And then you can invent something to improve it. You’d get glory and wealth and maybe earn a seat on the High Council,” she continued blithely, even as the Doctor slumped back against her desk.

“Someone else,” she groaned, rubbing at her tired eyes. She’d barely slept last night, worrying about Koschei Oakdown causing havoc in her lessons but she was starting to think she’d have preferred his chaos after all. At least the gossip columns she’d read had made it clear that the boy was both clever and interesting. U.N.I.T. students might be the former but they certainly weren’t the latter.

There was a long silence before a soft voice piped up from the back, “If you understand the laws of physics, everything that seems unexplained or mysterious makes sense. And if it doesn’t, then that’s even better. It could be something even more incredible. That’s why it's so interesting.”

She blinked. It was the boy she’d initially thought was Koschei Oakdown when he’d first walked in, only he was far too quiet and plain-looking to be the same maniac.

By now, the Doctor had seen enough photos online to know that the young Master was a brightly coloured mess with too many teeth, a terrifying smirk and the patchy stubble of a boy who thought beards were cool. And while the boy in front of her bore enough resemblance to be an Oakdown cousin, there was no chance he was the infamous Koschei - not with his beige shirt, gentle eyes and neatly lined up fountain pens.

“Interesting,” she said, “What do you mean by the unexplained?”

He paused nervously, biting his lip. The rest of the class was already giggling quietly. Whoever this kid was, she was already betting he was probably far cleverer than the lot of them put together. She knew the type. She _was_ the type. The outsider in their own home.

“Go on,” she said, hoping she looked encouraging instead of desperate.

He cleared his throat, “The unexplained could be aliens.”

The whole class immediately burst out into loud, mocking laughter, falling silent only when the Doctor slammed a textbook down onto her desk.

“Judging from everyone else’s reactions, I’d say you must be the only person here with an open mind. What’s your name?” she said.

“Call me Mast-”

“Name, not title,” she interrupted quickly. It was going to be hard enough teaching this class when Koschei Oakdown showed his face, let alone if she was worrying about whether one of Lord Rassilon’s offspring was sending complaining letters home about her. The less she knew about the students’ connections to Gallifreyan high society, the better.

“O,” he said, with a small smile, “Call me O..., Doctor.”

“Brilliant,” she grinned back. He was going to be a joy to teach; she could already tell. The problem would be his syllabus-indoctrinated, close-minded classmates. And Koschei Oakdown, if he ever turned up.

She turned back to the rest of the class, “There’s a whole universe out there and more. Physics helps us understand some of it, but it also shows us how much we don’t know. O’s right. There could be aliens out there. And don’t forget, we’d be aliens to them. It depends who’s on which end of the telescope.”

They weren’t sniggering anymore but none of them looked particularly interested either. She sighed and reached for the textbook.

“Alright, let’s get a shift on with... thermodynamics. Start reading from the top of page 13,” the Doctor pointed at a spotty blonde in the front row. As the girl’s monotone voice washed over the classroom, she sank down into the teacher's chair at the front of the class. This was going to be a long year.

*********************************************

By the time the Doctor had finished going through the first chapter of A-Level thermodynamics to the class, O had cast the textbook aside and was engrossed in scribbling in his leather notebook instead. She’d deliberately chosen to ignore it, seeing as he wasn’t disturbing anyone but she’d be a poor teacher if she wasn’t concerned.

“O,” she called out as the bell went at the end of the class, “Can I have a word?”

The rest of the class filed out, ignoring them both. Not a single person threw O a backwards glance. The Doctor winced in sympathy. She hadn’t had any friends at school either but at least she’d been too oblivious to notice. From the way O was gazing at her now, it was evident he was the soft-hearted, sensitive type. He was like a wide-eyed puppy that someone like Koschei Oakdown would kick across the playing field if he wanted to. Speaking of which - 

"I suppose you know Koschei Oakdown?" she said, "I think he's a relative of yours?"

He hadn't been expecting her questions, judging from the way he blinked carefully at her before finally nodding, "O is for Oakdown, that's right."

"I thought so," the Doctor sighed, "Do you know where Koschei is? I was expecting to meet him today."

O shrugged, clutching his textbooks to his chest, "I wouldn't like to say. He's quite unpredictable."

That wasn’t the answer the Doctor was hoping for but she wasn’t surprised. And if anything, she knew she ought be grateful; truancy was a problem she was used to dealing with. She'd spent all week picturing the classroom equivalent of a plane crash and it wouldn't have surprised her if he'd used a Bunsen burner to set all the furniture alight... but still, she couldn't shake off the feeling that Master Oakdown's absence was going to be a bigger issue than it seemed.

"Was that all you wanted, Doctor?" O's eyes were dark, yearning pools and the Doctor winced inwardly. Why was she worrying about a student who wasn't even here when there was one standing right in front who so clearly needed her help? Someone as special as O so clearly was.

“No, I also wanted to say, I think you're really impressive. There aren’t many people like you,” she said gently, “Those who aren’t afraid of what could be out there or what others might think.”

“Aliens are very, very interesting. I’ve read everything I can gather,” O said with sudden, sparkling enthusiasm, “I even have a complete set of Fortean Times in mint condition.”

“Of course you do,” the Doctor fought back a laugh, “I bet you’ve got quite the bookshelf.”

O chuckled softly before suddenly falling serious, “They mock me, Doctor. The others, I mean.”

“I’m sorry,” she said, feeling her heart twist at the sight of his sad, wide eyes. He reminded her so much of herself that it was like looking into a younger, lonelier mirror. “They’re afraid of what they don’t understand. It’s a flaw in us humans.”

He nodded but didn't reply. Instead he simply gazed at her as if he knew she still had more to say.

The Doctor was quiet for a moment, before she could find the words, “None of us know for sure what’s out there but the universe has a habit of surprising us. We’re all capable of the most incredible things.”

“And what about you, Doctor?" he said at last, "What are you capable of?”

“That’s easy,” she said, “Sometimes I see things need fixing and I do what I can.”

“Is that why you wanted to speak to me? Do you think I need fixing?” O was staring at her with big, cautious eyes.

“No, O,” the Doctor grinned at him brightly. Even though she'd only just met him, the answer fell readily from her lips, like a truth she'd known for years, “I think you’re brilliant."

And somehow, O's warm, open smile made all her lingering worries about the missing Master Oakdown float away.

**Notes for the Chapter:**

> I’m really bad with faces so this is entirely believable to me. I don’t recognise people I actually know until they’re jumping up and down waving and shouting my name...
> 
> And I know it doesn't earn the 'underage' warnings yet but I've tried to dribble in some hints of what's to come..
> 
> Smut soon? Yes, we all know what we are here for. This is meant to be for Noncontober after all.


	3. Chapter 3

**Notes for the Chapter:**

> Note the rapidly increasing total chapter count. This fic seems to be writing itself...

It would be another two schooldays before the Doctor met Koschei Oakdown properly. To begin with, the unexpected peace seemed like a blessing, and the second day of the school year started quietly enough. Since the Brigadier had only hired her to teach two A Level classes instead of the usual seven year groups, the Doctor had plenty of free time to spend tinkering away on her beloved TARDIS.

“You just need some fixing up, don’t you, old girl?” the Doctor murmured lovingly, as she gazed up at the car’s undercarriage.

She’d been underneath the TARDIS all morning, scraping salt crystals off its suspension frame. It was a task that most Gallifreyans didn’t bother with, let alone know needed doing. Centuries ago, they would take their cars to a mechanic once a year, but nowadays, manufacturers such as Turbo Accelerated Road Driving Systems, aka TARDIS, sold far flashier vehicles.

The latest models were capable of everything from self-cleaning to self-driving, and even self-redecorating, if one was willing to fork out for the much-coveted Chameleon Circuit. But despite all the jibes the Doctor had endured, the vintage Type 40 was an incomparable beauty in her eyes and as result, there was nothing more the Doctor loved to do than spend her days fixing the old banger up.

She’d first noticed the TARDIS when she started her undergraduate degree at Gallifrey Academy. Its bright blue paintwork had caught her eye through the science lab window and over the coming years, she’d watched its shine fade under the red dust of the summer sandstorms.

By the time the Doctor had earned her PhD, she was sure the car had been abandoned and so, she’d rescued it, telling herself she’d give it back if anyone asked. No-one had - not that she’d gone back to the Academy to check - and she’d even managed to drive the TARDIS all the way to New New Earth one winter.

“That was when we met Jack, remember?” she murmured to the TARDIS, as flecks of grimy salt crumbled down onto her goggles.

Captain Jack Harkness had been hitchhiking from Boeshane and the Doctor had given him a lift all the way to the Cardiff Rift Line, where he was visiting someone called Ianto. Knowing Jack and how he seemed to have met just about everyone, she wouldn’t have been surprised if he’d already crossed paths with Koschei Oakdown or at least knew someone who had.

“If I ring Jack now, he’d probably tell me to quit while I’m ahead,” she grumbled, feeling the knot in her belly tightening at the thought of Master Oakdown’s enduring absence.

The Doctor had stopped by the Brigadier’s office after dinner the night before to warn him that the young Master was definitely truanting, but the headmaster had only reiterated that he was sure the Doctor had it under control. Considering she really didn’t, the stress ball in her stomach now felt like a permanent feature she’d have to get used to.

“Like having two stomachs,” she mumbled, “A food stomach and a stress stomach.”

Since the TARDIS wasn’t sentient, the Doctor was in no way expecting a reply and so, when one came -

“What’s a stress stomach?” A pair of eyes glinted beside her.

\- the Doctor jolted upright with a startled yelp. Her forehead slammed against the exhaust pipe and suddenly, she was wildly scrambling along the gravel, before finally curling up into a pitiful, moaning ball beside the TARDIS.

“Doctor! Are you okay?”, O’s voice was soft with concern. His hands tugged the Doctor’s goggles from her head, but as soon as they were off, the Doctor crumbled back into the ground, swatting him away.

“O! Don’t sneak up on me,” she groaned thickly through her fingers, “Most people don’t just pop out of nowhere.”

“Maybe I’m not most people,” O said, “But I didn’t mean to scare you, Doctor. I only wanted to know what a stress stomach is.”

It was a few, silent minutes before the pain eased enough for the Doctor to reply. She flopped backwards, letting her hands drop heavily against the ground.

“Your cousin is giving a stress stomach and you’re giving me a headache,” she said, bleary-eyed and dazed.

“My cousin?” O was blinking down at her oddly and the Doctor smushed her face back into the gravel with another moan.

She wasn’t the most professional of teachers but still, it wasn’t kind to complain about someone’s family, to that someone’s face. Even if they’d inadvertently scared her witless by lurking about where they were least expected.

The Doctor rolled back onto her back with a huff, and dragged a dusty, oil-covered hand over her eyes. The sky was bright behind O’s head and she wasn’t entirely sure if the rings of light she could see were natural halos from the sun or if she should make a trip to the School Nurse’s office.

“I’m worried about Koschei,” she replied at last, “I like to know where my students are, at least.”

“Oh,” said O and the Doctor couldn’t help herself.

“That’s your name. Don’t wear it out,” she joked weakly. O only stared at her, and the silence quickly grew awkward.

“What are you doing out here anyway? Shouldn’t you be in class?” she said, pulling herself up so that she was sitting upright. The world was spinning a little but O’s smile was steady.

“Double free period,” he said, “Every Tuesday and Friday afternoon.”

“Good for you,” the Doctor said. She was starting to feel a little sour, especially now that she could feel a bump swelling on her forehead, “Best get to the library then. It’s never too early to start revising.”

Arguably, the second day of the school year _was_ too early, seeing as she’d barely taught O and his classmates anything yet, but thankfully, he didn’t argue.

“I hope you feel better soon,” he said at last, looking a little stung as he turned away but the Doctor only grunted, flopping backwards onto the gravel once again. It was just her luck that her Oakdown-free day had gone completely pear-shaped.

*******************************

The Doctor spent the rest of the afternoon bored on her sofa with an ice pack on her forehead. At first, she’d tried to keep working on the TARDIS but the bump had swollen quickly, before purpling and then her whole head had started throbbing.

Soon, she’d been forced to call it quits, and had retired to her flat with a packet of custard creams and a book on primitive code-breaking she’d picked up during her last trip to New New Earth.

She’d eaten over fifty biscuits and read the book twice before falling asleep on the sofa. She would have probably slept straight through to morning if whomever was at her front door would simply stop knocking and go away.

“O,” she sighed, blinking at the boy in front of her, “What are doing here?”

He was clutching a tub of Rokhandi Floss ice-cream and a tiny, silver tin, and staring at her beseechingly, “Can I come in?”

“I don’t know. Can you?” she said, still a little dazed with sleep. Every school had different rules about where students were allowed to go within school grounds but she was fairly sure that the teachers’ block was always off-limits.

“Sixth-formers are allowed. Detentions are always in the teacher’s living quarters,” O said, stepping carefully past her and heading towards the kitchen.

That seemed a little unusual but before the Doctor could question it further, O was handing her a bowl of ice-cream and a spoon he’d swiped from her own cutlery drawer.

“I noticed you weren’t at dinner,” O said, settling onto the sofa that she’d been asleep on moments before, “I was worried I’d really hurt you.”

His eyes were huge and round with guilt, and the Doctor’s heart immediately plummeted with her own. O hadn’t meant to startle her and then she’d dismissed him so coldly when he’d only wanted to chat. It wasn’t the best way to treat the only student she actually liked so far at U.N.I.T.

“It was an accident,” she said firmly, “And it’s not that bad. It’ll be gone in a few days.” She poked the bump on her forehead gingerly.

O nodded, smiling at her warmly, “I might be able to help with that, once we’ve finished this.” He gestured at bowl in her hand with the one in his, then glanced up at her again, nervously.

She sighed. To be fair, she _had_ missed dinner and he _had_ brought one of the nicer brands of ice-cream. Rokhandi Floss was famously so good that even unruly children would behave at the promise of a scoop, or so the slogan went.

“I s’pose some sugar can’t hurt,” she said, as she sat down, wondering idly if she could placate Koschei Oakdown with ice-cream, if he ever showed up.

It was strange to remember the two boys were related. She glanced sideways over at O who was sprawled out messily on one side of the sofa, the silver tin he’d been holding tossed carelessly onto the empty, middle seat between them. Aside from the physical similarities, O seemed nothing like the cousin she’d read about and -

“Tell me about N.A.S.A.,” O said, interrupting the Doctor’s train of thought, “The Brigadier said you worked for N.A.S.A.”

And with that, any lingering sense of unease over whether or not O should be in her flat evaporated. What was more natural than a U.N.I.T. student wanting to know more about the scientific career path ahead of them? Especially when they had teachers like the Doctor, who had so many stories to tell.

A broad grin spread across her face, “I wasn’t exactly working for them. It’s fairer to say that they were working for me.”

There weren’t many 17 year olds who paid attention to the intricacies of Gallifrey’s space explorations, let alone neighbouring New New Earth’s, and yet, O was able to follow her anecdotes with ease. It wasn’t long before she’d told O all about the work she’d done on Project Silence and listed out all the amazing things one could really do with a shuttle signal.

His eyes even lit up when the Doctor dropped in that her time with N.A.S.A had included a trip to the Oval Office and that she’d sat in Nixon’s chair.

“Was that allowed?” O said, “Given its age?”

“I’ve never been one for rules,” the Doctor grinned, “Just because something’s old doesn’t mean it’s off-limits. And I was having fun!”

At that, O’s smile shifted strangely, but then the Doctor was off again, rambling about New New Earth’s first moon landing and how exciting it was to witness them finally catch up with Gallifrey.

O was the perfect audience. He nodded at the most interesting parts, and his questions were both precise and incisive. And even though it had only been a few weeks of the summer holidays, it’d been an age since the Doctor had had a chance to talk to a student who really _listened_ the way O did.

Soon, the Doctor had forgotten all about her aching head, or whether or not O should be in the teacher’s block. She’d even forgotten what time it was, thrown off first by the nap she’d had and now, by how much fun she was having, showing off to someone who _wanted_ to be shown off to.

It was only when she’d finally rambled through the last anecdote she had about N.A.S.A that she realised how close O had shifted to her. He’d fallen silent a while back and now, he was gazing at her like her face was sprinkled in stardust. And then, before the Doctor could shift away, or even wonder why O was so close -

He was kissing her. And she froze.

And every remaining memory of space shuttles and moon landings flew away; suddenly, she was only conscious of O’s lips on hers and the tip of his nose pressed awkwardly against her own. And then, surprise barrelled into panic but somehow, pulling away only brought O tumbling closer, until his head was perfectly angled against hers.

Then O’s mouth was opening up, his breath hot on her lips and most alarming of all, his tongue was probing softly, coaxing her own mouth open too and still, the Doctor was frozen, completely unmoving except that -

She was kissing him back.

It was like her body was on auto-pilot. The hand she’d lifted up to push him away had only curled up uselessly in the collar of his shirt and everything was spinning, like she’d finally developed concussion, hours after hitting her head.

At first, the teen’s movements were clumsy and uncertain but then, O seemed to gain confidence out of nowhere. He’d shifted even closer until she could feel the weight of his body pressing into her. His tongue was soft and curious and she was drowning.

When O finally pulled away from her, his pupils were wide and dilated.

“I’d better go,” he said, his eyes still fixed on her mouth even as he stood up, “It’s almost lights-out. The Brigadier’s always stricter about bedtime at the beginning of term.”

The Doctor only stared at him, wordless and limp. There were a hundred reasons why she should get up and march O to the Brigadier herself...

But her body still wasn’t obeying her brain and she could only watch, mute and numb, as O leant down to drop another kiss on her lips.

“I made this for your head. Use it before you sleep,” he said, and she was only distantly aware that he was pressing something into her hands. And then, O was gone.

It was an age before she could move again and when she did finally look down, her hand was clutching the expensive-looking tin O had arrived with.

There was no label and it was a sign of how out-of-sorts the Doctor felt that she wondered, as she twisted blankly on the lid, whether she was opening some sort of tiny explosive. But the tin was only filled with a sticky, purple ointment that made her fingers tingle when she dipped them inside. It seemed harmless enough, although the Doctor still wasn’t exactly sure what it was and then, she spotted it; on the underside of the lid, scrawled in permanent marker, O had left a message.

_a present for my newest friend_

The Doctor slumped back into the sofa, the now-familiar feeling of dread knotting in her stomach once again. She’d been worrying about entirely the wrong person. The nightmare waiting for her at U.N.I.T. hadn’t been Koschei Oakdown; it had been O.

**Notes for the Chapter:**

> Comments and kudos are very much appreciated. Especially as we are in niche territory here :-)


	4. Chapter 4

**Notes for the Chapter:**

> Before you read this, I want to say, don't try this at home!

The Doctor’s third day at U.N.I.T. began very much like her first, only now, instead of dreading meeting the young Master Oakdown, it was O she didn’t want to see. Unfortunately for her, she couldn’t exactly avoid him - not unless she bailed on both her Physics and her Chemistry classes, but that wouldn’t be fair to all the students she _hadn’t_ been kissing.

If it hadn’t been for O and his ill-judged kiss the night before, the Doctor’s mood would’ve been entirely more cheerful; she’d prepared a practical that was a particular favourite of hers and it was one she was _sure_ would waken any latent scientific wonder in her new students.

It was also a class the Doctor would have thought twice about teaching if Koschei Oakdown _had_ shown up but thankfully, he was still bunking off and at this point, she was too worn out from fretting over O to worry about the young Master’s absence anymore. Anyway, from what she already knew about Koschei Oakdown, he was the only student in her class who _wouldn’t_ benefit from learning how to make fireworks from scratch.

“And that is how you make a Rassilon Wheel,” the Doctor finished flatly, her goggles hitting the desk with a dull thunk.

She’d been demonstrating the most difficult parts of the practical for the last half hour and it was the first time in her teaching career that she’d hated having so many eager eyes on her. Even though she’d been trying valiantly to concentrate on potassium powder and inner tubing, the Doctor had spent every minute acutely conscious of O’s eyes roving over her face.

The ointment he’d given her last night had worked perfectly, despite its obvious homemade origins. The sticky purple goo had made the Doctor’s tongue tingle pleasantly and so, figuring that it probably wouldn’t kill her, she’d swiped the rest liberally over the bump on her forehead.

By morning, not only had the swelling gone, the bruising has disappeared entirely. It was as if yesterday’s events hadn’t happened at all, if only O would stop staring at her.

“Everyone pair up and pick one type of firework to make between you,” she ordered testily, “If you’re with me for Chemistry next, you can make a second.”

There was a collective groan from the half who weren’t doing double science, before a flurry of chairs scraped across the floor and the students rearranged themselves within their friendship groups. She should've been pleased they were so keen, but the Doctor only fiddled awkwardly with the straps of her goggles, pretending not to watch O as he weaved across the classroom to tap on Miss Osgood’s shoulder.

Petronella Osgood was a dorky girl with thick, rectangular glasses and a practical ponytail, and although the two didn’t appear to be particularly good friends, she seemed thrilled enough to have a lab partner, judging by how quickly she scuttled across the classroom to sit beside O.

The Doctor’s eyes wandered over the rest of the classroom. Most of the pairs were arguing over whether to make Rassilon Wheels, Shuttle Rockets or Omega Candles, but a few had begun gathering supplies from the store cupboard. Miss Osgood had already grabbed the entire roll of purple tissue paper and O was... doing whatever he should be doing in his A-Level Physics lesson and he didn’t need his teacher’s attention.

The Doctor fixed her eyes on her own desk, staring intently at a gnarly knot in the wood. It was best to give O the cold shoulder for a few days and then the awkwardness would fade; he’d only developed a crush and it was harmless as long as she ignored him.

After all, O was a sweet, lonely boy at the most elite school in Gallifrey, his cousin was an infamous hellraiser who’d been missing for days and he’d latched on to the first person who’d said a nice word to him.

The best thing to do would be to forget the kiss had ever happened, the Doctor resolved. It was a one-off. If she hadn’t been so dazed by her head injury, she’d have realised sooner that O had gotten the wrong idea. There was no point embarrassing them both by reporting it to the Brigadier and anyway, he’d kissed her first. It wasn’t like she’d done anything wrong.

Except she _had_ kissed him back, the Doctor’s traitorous mind whispered and then, with the sense memory lancing through her like a knife, she couldn’t help but look over at O, who of course, was already looking back.

*****************

Four hours later - after the students had had their dinner and once the Doctor had made a few, _tiny_ adjustments to their practical work - the entire Year 13 cohort was huddled on the playing fields behind U.N.I.T.

The Doctor hadn’t expected more than the forty five she taught but she wasn’t about to turn the other hundred away - not when they were all buzzing with delight, as the sky above lit up in a dazzling array of colour and sound.

She did the actual igniting herself, with the aid of a long pointy stick because she wasn’t _entirely_ reckless, and soon, the Doctor was whooping along with the crowd, dishing out merits for the fireworks that were especially loud or impressively bright -

Except for O and Osgood’s Double Rassilon Wheel. While the other students gasped at the inventive, perfectly executed twist on the single wheel they’d been taught, the Doctor was mute. She only gulped up at the sky in reluctant burning admiration, before ducking down to light the next fuse.

The truth was, she still felt too nervous to even look at O, let alone praise his work, even though it really was brilliant. All evening, O had been doing an outstanding job of pretending to be interested in the explosions above them, but it was obvious to the Doctor that his attention was really on her. Of course, it was only obvious because hers were also fixed on him.

She scowled up at the smattering of sparks shimmering amidst the smoke. In that moment, with the weight of O’s affections pressing down on her, she’d have given anything to be dealing with Koschei Oakdown’s antics instead.

*********

She woke to bursts of thunder overhead. The sound was relentless and alarmingly close and for a frightening moment, still dazed with sleep, it felt like the storm was in the room with her, perhaps even _was_ her.

The Doctor groaned as she fumbled blindly for her alarm clock, wading through mind fog to squint bleary-eyed at the numbers glowing out of the darkness. It was exactly midnight on the dot when another spectacularly loud _something_ exploded overhead.

And then she was leaping out of bed with the kind of blind panic that only came from being the teacher who had taught forty five gifted students how to make their own fireworks that very afternoon.

By the time the Doctor had found the door to the fire escape, confusion had set in. The science store cupboard was calibrated to her personal biometrics, at least fifty fireworks had gone off above her already and thankfully - confusingly - it didn’t sound like anyone had been hurt.

It took a frighteningly long minute for the Doctor to scramble up the staircase to the top of the teachers’ block. When she finally tumbled, panting, onto the flat concrete rooftop, the sky was bright and thick with clouds of smoke. Fireworks were still exploding overhead in an array of red, purple and pink. It was utter chaos in every sense of the word and yet, the Doctor only cast a cursory glance upwards before turning toward the lone figure on the far side of the roof.

He was a wild thing, leaping, clapping and screaming up into the sky. She couldn’t see his face but she didn’t need to; he was the nightmare she’d wished for only hours earlier, when she’d wanted the problem with O to go away.

“Master Oakdown,” Her voice was weak and brittle under a fresh burst of Shuttle Rockets above them. They exploded, one after the other, tinging the air a blinding bright purple. Smoke was pluming in circles overhead as the young Master swayed beneath them, as if hypnotised by his own work.

“Master Oakdown,” She was louder this time but still, there was no reaction.

With the span of the roof between them, it was impossible to tell if he couldn’t hear her or if he was simply ignoring her and so, with full-blown desperation coursing through her, the Doctor threw formality out of the window.

“Koschei!” Her scream cut through the air like a sword slicing through flesh and finally, _finally_ , he spun round to face her.

And in that very second, the Doctor would’ve sworn that the entire universe was turning upside-down and inside-out because, while the boy looking back at her was definitely Koschei Oakdown, he was also -

“O,” she choked out, her hand reaching up to her own mouth in horror. The mouth O had kissed. The mouth she’d kissed Koschei Oakdown with -

“You can’t be,” She was shaking now.

“Oh, I can be. I very much am,” He slinked towards her, his smile all teeth.

And then, his fingers were digging into her arms, holding her upright as she stared frozen into a pair of dark, sharp eyes. She felt like she was fainting or maybe having some sort of strange nightmare after a stressful day, except she was definitely awake and -

“You’re Koschei Oakdown,” she whispered.

O’s gaze flicked sideways for a long, horrifying second. When he finally looked back, the smirk that she’d only previously seen on the front page of the Gallifreyan Weekly was wide and gloating across Koschei Oakdown's face.

“Got me,” He winked and then he was gone.

**Notes for the Chapter:**

> Is it still a dramatic reveal if we all knew it was coming????
> 
> ps Happy (early) Bonfire Night!


	5. Chapter 5

**Notes for the Chapter:**

> I’m finally leaning into the school tropes!

The Doctor didn’t react well to finally meeting Koschei Oakdown. In fact, she didn’t react at all, only staring blankly at the space where he had been and at the mess of matches and spent fireworks he’d left in his wake.

She probably would have stood there all night, if the school caretaker hadn’t arrived with two large buckets and a directive from the headmaster to go straight to his office.

“Did the Brigadier say why?” she asked numbly, but Nardole only grumbled something that sounded a little like no-one-ever-tells-Nardie-anything, so she left him throwing water over the remains of Koschei’s chaos

The walk across the U.N.I.T. grounds was over far too quickly. The Doctor only had enough time to feel her stomach lurch sickeningly as she replayed how O’s soft smile had morphed before her eyes into Koschei’s cunning smirk. The kiss they’d shared had been bad enough before and now, unbelievably, it was so much worse.

Steeling herself, she rapped reluctantly on the Brigadier’s office door. The now-familiar urge to run away was bubbling away inside her, but the very least she could do was make sure the headmaster sent someone after the young Master. And she should probably explain why she’d taught a literal juvenile delinquent how to make fireworks by hand.

“There you are, Doctor.” The door swung open to reveal the Brigadier, somehow still radiating authority, despite his woolly dressing gown and fluffy slippers, “There’s been a Code Red.”

She winced, “I’m so, so sorry. I-“

But her confession was cut off by a smug voice from within.

“Do relax, you two.” Koschei was lounging in a chair in front of the headmaster’s desk, as if he _wasn't_ in trouble.

“Show some respect, Master Oakdown,” the Brigadier’s rebuke was surprisingly mild, “The Doctor’s here, exactly as you asked, so what do you have to say for yourself?”

“Nothing. I’ve changed my mind. I’m very changeable, you see,” Koschei smirked. He was indeed unrecognisable from the boy he’d been before.

“You asked for me?” the Doctor echoed, brain stuttering pointlessly over the least helpful fact of the night.

“Well, I couldn’t very well let you stay up there until morning. Not in _that_ outfit.” Koschei’s dark eyes raked over her bare arms and legs.

Until that very moment, she hadn’t known that it was possible to feel so stupid, so indignant _and_ so exposed at the same time. While Koschei looked like the future Lord he was, in matching deep purple silk pyjamas, the Doctor was wearing a grey t-shirt that she’d picked up in a charity shop. Even worse, he clearly found her favourite question-mark-themed boxers hilarious.

“Is that a choice?” he asked, mouth quirking in amusement, “I don’t mean to pyjama-shame you.”

“They’re unisex,” she snapped, yanking down at the hem of her t-shirt, but he only grinned with even _more_ teeth.

“Enough. It’s almost 1am,” the Brigadier interrupted impatiently, “I’m getting too old for this sort of thing. He’s all yours from now on, Doctor.”

“What?” She blinked. That was the last thing she’d expected him to say but he was already ploughing on.

“Detention every evening for a week,” the Brigadier said, oblivious to the Doctor’s jaw dropping.

A week’s detention was better suited to a fight in the playground or careless behaviour during a science practical. It was _not_ an apt punishment for buying dangerous explosives while underage, trespassing onto the roof of the teachers’ block and _then_ disturbing the peace. She was about to interject when -

“The Doctor will supervise,” he finished, “Starting tomorrow.”

Her mouth snapped shut. Suddenly, a week sounded like _plenty_.

“Off to bed now, Master Oakdown,” the Brigadier added tiredly, “And do try not to wake anyone else up or I’ll be sending Nardole to lock you in.”

Koschei didn’t seem fazed by either the punishment _or_ the threat. Instead, he sauntered out with a pleased swagger, even throwing the Doctor a wink as he brushed past. The door swung shut behind him, leaving her stunned.

He’d given her no choice. Now more than ever was the moment to tell the Brigadier that O had kissed her - _that Koschei Oakdown had kissed her_ \- and that she was out of her depth. He’d already fooled her once and she couldn’t help him learn to be good; she simply didn’t know how. She rolled the failure on her tongue, but before she could begin -

“You must have made quite an impression. Fireworks instead of actual fires!” The Brigadier actually sounded pleased, “It would’ve been a very different story six months ago. I made the right decision calling you in.”

And with the headmaster’s admiring eyes on her, the Doctor’s heart sank. Of all the things she disliked doing, letting down a friend in need always hurt her most.

“He’s troubled,” she said, uncertainly.

“He’s young,” the Brigadier corrected her brusquely, “And if anyone can steer him onto the right path, it’s you. What do you say, Doctor? Seven detentions?”

She could feel her resolve crumbling away. After all, the Brigadier had brought her to U.N.I.T. because Koschei needed her help. What kind of person would she be to abandon him now? Either of them.

“I'll do my best, but I can't make any promises,” she said at last.

After all, now that she knew who Koschei was - or wasn’t - he no longer had the upper hand. He’d had his fun and now his games would end. She’d make sure of it.

“As long as you can sort out Master Oakdown, the rest will take care of itself,” the Brigadier said, and with that, he ushered her off to bed.

***********  
The next day passed in a blur. It was hard to believe it was only the Doctor’s fourth day at U.N.I.T. when she already felt so battle-worn. Thankfully, it was a relatively easy teaching day; she’d tasked the students with writing up the lessons learnt from the fireworks practical, reflecting on what had gone well and what they could’ve done better.

Once they’d settled into their pairs, chattering happily about whose firework had exploded best, the Doctor slumped behind her teacher’s desk at the front of the classroom. She couldn’t help but ruminate on the same questions she’d set them, but with an Oakdown-shaped twist; What, if anything, had gone well with O? What could she do better with Koschei?

Unfortunately for the Doctor, tiredness and an abject sense of worry had set in and soon, all she was really doing was moping. It also didn’t help that the placement of her desk gave her the perfect vantage point from which to observe the young Master in light of the new data.

It was obvious now that the others hadn’t been excluding O because he was a geek who believed in aliens; they were avoiding Koschei because he was a lunatic who believed in aliens _and_ was prone to fits of anger and destruction. That said, the young Master was behaving well-enough now. If you could call him monologuing while Miss Osgood scribed ‘well-enough’.

“Detention,” the Doctor snapped suddenly.

Thirty pairs of eyes stared up at her blankly.

“Detention, Miss Osgood,” she cleared her throat, “You’re meant to be working in pairs, not writing Master Oakdown’s report for him.”

There was an uneasy murmur as the students absorbed her quite frankly ridiculous punishment, but no-one protested. Koschei only raised an amused eyebrow before picking up his monologue and, after his pointed elbow in her ribs, Miss Osgood continued scribbling. The only difference was that now the poor girl kept throwing nervous glances at the Doctor in-between paragraphs.  
  
The Doctor scronched her nose at the textbook in front of her. She could hardly dish out a second punishment for the same non-offence and anyway, she’d gotten what she wanted; Miss Osgood would be her unwitting chaperone during that evening’s detention with Master Oakdown. With any luck, having a friend-of-sorts around would keep him entertained enough to prevent him toying with her any further.

*****************

The Doctor had been completely mistaken about Petronella Osgood and Koschei Oakdown’s friendship, which was no surprise considering her track record at U.N.I.T. so far.

It turned out that Miss Osgood was less of a respected classmate and more of an intelligent minion. It was a testament to the schoolgirl’s brilliance that the young Master even acknowledged her but it was unlikely that she saw his tolerance as a compliment.

They’d arrived at the Doctor’s flat ten minutes before detention was due to start, and it was exactly when they knocked that she realised she’d forgotten to find out if what O - _Koschei_ \- had said was true; it seemed unlikely that detentions would be held in a teacher’s living quarters, even those with Sixth Formers... but Miss Osgood didn’t seem at all perturbed by the location. In fact, she only seemed concerned by Koschei’s cat-like hissing and soon, the Doctor’s guilt had grown too big to ignore.

“Alright,” she sighed, “Why don’t we call it a night?”

Miss Osgood fled without so much a second glance but as the Doctor expected, Koschei didn’t move from his seat opposite her at the dining table.

“But there’s another hour left of detention,” he cocked his head at her, “Or should I tell the Brigadier you’re not punishing me appropriately?”

He giggled gleefully, as if it wasn’t her career - _her reputation_ \- on the line and with that, something in the Doctor finally snapped.

“Why did you do it?” she snarled, teeth clenching in sudden, thrumming fury.

Her anger startled him and he sat up straight for the first time that evening, eyeing her with renewed interest.

“Do what?” he said. He was goading her and she knew it.

“Why did you lie?” Her tone was completely unprofessional now, but she really didn’t care anymore.

“Not telling you,” His laughter was abrasive and his expression the exact opposite of how sweet it had been when he’d kissed her, “Go on, crack a smile.”

It seemed almost impossible to fathom that he’d ever been O or even imagine why he’d pretended to be and somehow, his smugness rankled even more.

“Proud of yourself?” she sounded bitter, even to her own ears, and infuriatingly, she could see how much it pleased him.

“Ecstatic,” he said and then, he was standing, snaking his way towards her with an expression that reminded her starkly of an animal stalking his prey. Which meant she was the prey.

She rose to meet him. They were exactly the same height, though he would probably gain another inch by the end of the school year if he was lucky. But for the moment, she could still look Koschei directly in the eye and watch the smug glimmer in his gaze shift into something darker and more brooding.

“All these games make you happy?” Her anger had reached boiling point and if she could’ve hit him, she would have.

Thankfully, he came to a standstill a foot away from her.

“It’s not a game,” he replied. His smirk had vanished and suddenly, he was sullen and serious.

“Then why did you do it?” She was repeating herself now, and she probably sounded a little hysterical. She certainly felt it but he only shrugged, unfazed.

“You assumed,” he said.

“No,” She gestured in frustration at his outfit, “Your clothes were different. Your hair. Your... everything.”

In his tailored navy shirt, fitted waistcoat and matching chequered trousers, he looked nothing like plain, ordinary O.

“Well done,” he hummed flatly, “Got me. I knew the Brigadier had sent for you to keep an eye on me. I figured I’d extend the hand of friendship first.”

“So you pretended you were O to spy on me? Pretended you believed in aliens, that you were interested in...” she trailed off. Her anger was cartwheeling into humiliation.

“Pretended I was interested in?” His smile was back and embarrassingly knowing, but he wasn’t gloating anymore. Instead, he looked almost like O again, nervous and yearning and this time, she knew what was coming.

When he stepped towards her, she darted away smoothly, and then, somehow knowing he would try again, she hopped onto the tabletop behind her, sliding backwards until her knees were spread wide and Koschei was left standing mournfully between them.

“Ha!” she crowed, but her triumph fell lamely between them. 

“I thought we were friends,” His arms hovered in the air in a parody of innocence, except there was now barely six inches of space between them and even though they weren’t touching...

Her hands landed on his shoulders, locking him firmly in place, “I’m your teacher and we should really have a proper chat.”

She paused, wondering where to start. She needed to draw a line under the kiss and make sure he knew how inappropriate he’d been - how inappropriate he was _still_ being. She should say something that would assert her authority over him and remind him that there were boundaries he couldn’t cross. Lastly, she wanted an explanation for his fireworks fiasco, if not the -

“Why did you kiss me?” It wasn’t what she’d intended to say, and yet the words had flown out her mouth.

“I just couldn’t help myself,” he sounded so earnest that she almost believed he really was that sweet - as if everything about Koschei Oakdown wasn’t meticulously calculated - and then he suddenly _was_ that sweet boy again.

“Do you like me more when I’m O?” he said, with wide puppy dog eyes and a trembling lower lip.

“No!” the Doctor choked and then she froze.

Her hands had curled up in reactive horror, fingers twisting into his shirt collar just as they had when he had kissed her the other night. He’d ducked his chin downwards in a pretence of shyness and suddenly, the already tiny space between them seemed to have disappeared entirely under the length of his ridiculously long eyelashes. The tip of his nose brushed against hers and the sudden - _familiar_ \- proximity made a strange feeling of hurt bubble in her chest.

She’d liked O. She’d liked him a lot, and even though his little crush had panicked her, she’d also been flattered by the attention. Hadn’t he been so interested in her stories? And wasn’t it so impressive he’d made her that healing tincture? Had Koschei really gone to all that effort just to trick her?

“No,” she said, softer this time, “That’s not how it works. You can’t split off parts of yourself and call them something else. Deep down, you’re the same person. You are you who are and you like what you like.”

“Yeah I do,” Koschei leered dramatically but it was so overdone that he started snickering even as he said it and then, to her surprise, the Doctor found herself laughing too and just like that, the tension between them was broken.

This time, when he leaned towards her, pressing his forehead gently against her own, she didn’t pull away. Instead, she only watched quietly as his hands dropped onto her knees and then drifted upwards to rest halfway up her thighs. His nails scraped lightly at the fabric of her blue trousers and the heat of his palms burned through to her skin beneath, but still, she did nothing.

There was something hypnotic about Koschei Oakdown, when he wasn’t leaping about causing chaos. On the one hand, his intensity was terrifying and talking to him was like dealing with a wild cat who was liable to spit and scratch at any moment. On the other hand, she’d been a teacher long enough to know that the unruliest students were often the most sensitive and that she should seize the calmer moments when she could.

She watched as his face settled into an expression that was neither completely innocent or utterly gloating. At last, he seemed to be showing her the boy behind the masks.

“It wasn’t a game. I wanted you to see me, not the story of me,” Koschei said at last. “And you’re right. I really do like space. I want to study Cosmic Science next year. Maybe at the Academy.”

“That’s what I did,” she said, suddenly pleased and more than a little relieved. She’d been right after all. That feeling of recognition she’d had when they'd been talking about space travel and aliens, and the way he’d lit up too - she knew they were the same.

“I know. I looked you up,” he grinned but this time, somehow she knew he was only teasing, “Late developer, were you?”

She sniffed, pretending to be offended, “My degree classification was fine, thank you very much. They lacked imagination.”

“I’ll do better than fine. I want to master everything,” he paused, dramatically, waiting for her to meet his eyes before continuing, “I also really, really like explosions.”

“Yes, I noticed,” she snorted, amused despite herself, and then because he seemed to be in a sharing mood, “Where _did_ you get those fireworks from?”

Although she’d only spent an evening with O, she fancied that he’d have ducked his head shyly at her question, but Koschei only smirked with pride, “My dear Doctor, you taught me yourself.”

It was in that moment that she realised that there was something deeply wrong with her. She should’ve been furious. If he’d truly made them all himself, that meant he’d hacked through the biosecurity locks on her classroom store cupboards as well as stealing an obscene amount of restricted chemicals. And then, there was the danger he’d put himself in -

“You could’ve hurt yourself,” she blurted out.

Koschei’s eyes widened. Her concern had caught him off-guard, “I did good though. They were brilliant. Go on, admit it.”

And it was true. They’d been so good that she’d thought he’d bought them; she hadn’t once considered he might have actually _made_ them. 

“They were. _You_ were,” she allowed, “It must’ve taken hours. Why did you do it?”

“Isn’t it obvious? You’d been ignoring me all day,” he said, “How else would I get your attention?”

“You’re crazy,” she gasped before her teacher brain caught up and she scrambled to rephrase her horror less harshly, “I mean, that’s crazy. Don’t do that again.”

“But I wanted your attention,” His eyes were so wide and needy that it made the Doctor’s heart pang sharply. 

Koschei Oakdown wasn’t the lawless wretch everyone else said he was. The boy standing in front of her only seemed lonely and a little lost, and hadn’t the Brigadier brought her in for this very reason? She could help him. She was certain of it.

“You’ve got it,” she said softening, “If you want my attention, you can ask for it. But no more explosions, okay?”

“Okay, I’ll ask,” He was smiling again, eyes alight with a playfulness that was now familiar, “I’ll start now.”

She had a sickening feeling she knew exactly what he was going to say so she wasn’t at all surprised when his lips brushed against hers.

“Will you kiss me?” he said and she did.

**Notes for the Chapter:**

> I’ll leave you to imagine exactly how long they spent kissing but Koschei did drop a hint. Maybe you spotted it?
> 
> I always love reading your comments and I’ve had a particularly hard week as I’ve been unwell so I’d especially love to know if you liked this chapter. <3


	6. Chapter 6

**Notes for the Chapter:**

> I noticed the Spyvember prompt was 'Road Trip' so I scrambled to post this. Overall, it's taken me like 100 hours to write so if you could just pretend you've read it a hundred times to make me feel better/ less like I need to get a real life, that'd be appreciated. 🙈

From then on, Koschei Oakdown had the Doctor wrapped around his little finger and she knew it. In the cold light of day, she couldn’t believe how stupid she’d been. She’d read every tabloid article written about the young Master and she’d seen first-hand how much he enjoyed his games so how could he have played her? _Again_. And how could she have kissed him? _Again_. This time, she was entirely to blame and now, she had everything to lose.

Which was why the Doctor didn’t argue when Koschei arrived five hours too early for his second evening of detention. She’d already known that he had free periods on Friday afternoons - he’d told her so himself, when he’d been pretending to be O - and since the Doctor was teaching literally half of Koschei’s classes, if he was free, he knew she would be too. And so, she let him in with a defeated sigh.

In any case, there was no point delaying any further. She’d already spent the morning carefully avoiding Koschei’s gaze during both Chemistry and Physics but he’d bounced around happily regardless, as if energised by all the _attention_ he’d gotten from her the evening before. Which meant he’d probably already plotted out all the different ways he was going to blackmail her for the rest of the school year.

The Doctor glared at Koschei miserably, waiting for him to name his terms... but none came. Instead, he only stared at her, his expression thoughtful and oddly caring, a little like O’s had been when she’d banged her head on the underside of her car.

“What if we work on your TARDIS?” Koschei asked suddenly.

“What?” She said dumbly. It wouldn’t have surprised her if her luck was so bad that Koschei was somehow the only telepathic human on the planet.

“I’ve seen what you’ve done,” he continued breezily, “I mean, it's good but it's not great. I’ve got notes.”

His arrogance made her eyes roll, but it turned out that the young Master did indeed know his way around a Type 40 TARDIS. He’d given himself a supervisory role for the afternoon but his directions were precise and surprisingly helpful, and the Doctor soon found herself lying on the gravel, staring up at the car’s beam axle with begrudging admiration.

“Mine’s custom-made,” Koschei bragged cheerfully, a disembodied voice above her, “I built it myself.”

It didn’t surprise her to learn that the young Master Oakdown had once owned ‘a TARDIS or ten, I never counted’ or that he’d grown up racing them around his father’s estate. It was even less surprising to hear that he’d cannabalised them all one summer to make his own bespoke TARDIS that he’d called ‘The Paradox Machine’.

“It shouldn’t have worked but it did,” Koschei explained proudly, “I drove it all the way to New New Earth.”

That was where his anecdote took a less charming turn.

“I ran over a freak in a stupid coat who tried to flag me down for a lift. He wouldn’t get out of the way and I couldn’t resist. I just had to hit him,” Koschei sighed dramatically, “He got back up again like he was immortal or something. I should’ve reversed and run over him again.”

The screwdriver slipped out of the Doctor’s hand with a clatter. Every time Koschei impressed her with his brilliance, he turned around and revealed something utterly horrifying. And even worse, his story sounded alarmingly familiar.

Hadn’t she met Captain Jack Harkness when he’d been hitchhiking to New New Earth? He’d told her all about being ‘on the wrong side of a hit-and-run against a purple fiend’. She was about to ask if the immortal had been handsome or tried to say hello when -

“Look out, it’s the Brigadier,” Koschei said, “Mind your head.”

The Doctor scrambled out from under her TARDIS, shooting Koschei an exasperated glare. For someone who was so utterly horrifying, he could also be surprisingly endearing. He was making her head spin.

“Master Oakdown, what do we have here?” the Brigadier said, eyeing Koschei who was lounging on a work bench.

“I’m helping the Doctor,” Koschei said, all wide-eyed innocence. It was bewildering to watch his performance from the outside.

“Very good,” the Brigadier nodded, as if Koschei’s fireworks fiasco hadn’t happened less than two days ago.

“That’s what the Doctor said,” Koschei said, “I get a reward if I’m good.”

“What’s that then?” The Brigadier sounded intrigued, peering down at the Doctor where she still sat sprawled out on the gravel.

Instead of responding, she only stared up at Koschei in horror. This was it. The end of her career and a lifetime sentence in Stormcage Prison for being stupid enough to kiss an underage student. _Twice_. But he only chattered on smoothly.

“The Doctor’s going to drive me into town. I’ve a shirt that needs tailoring,” Koschei said, perfectly sweetly.

“Excellent idea,” the Brigadier nodded, “Give the old girl a spin. I’d appreciate a bottle of Sentarion Rekkar if you can find time for a pit stop, Doctor.”

Caught between the Brigadier’s unsuspecting approval and Koschei’s deceptive smile, the Doctor responded the only way she could.

“That’s fine,” she grunted and then she was crawling back under the TARDIS, fuming silently.

****************

The problem was, it was impossible to stay angry with Koschei for long. Giving him the silent treatment didn’t work; he simply jabbed and stabbed until the Doctor retaliated. After that, since she’d already engaged with his infuriating chatter, the conversation inevitably ended up somewhere interesting, and soon, she’d forgotten to be angry at all.

It wasn’t long before they were comparing adventures from their summers in New New Earth. Although Koschei claimed to detest the place, moaning at length about the stink that permeated New New London, he’d spent an inordinate amount of time there. It was easy to forget how young he was when he had so many stories to tell.

It also didn’t help that driving off without a destination in mind was one of the Doctor’s favourite pastimes. It didn’t take long to pick up the Brigadier’s Rekkah from the first town they drove through and after that, they had the whole afternoon ahead of them. Despite everything infuriating about the situation, the Doctor was having fun and so was Koschei.

He’d nudged her out of the driver’s seat with ease. The Doctor hadn’t wanted to ruin the mood by refusing him and in any case, she didn’t have a reason to, even without the memory of kissing him burning on her lips.

“I’ve got my provisional license,” Koschei said, “So I can drive if you’re with me. You’re my responsible adult.”

He’d beamed at her angelically, as if he hadn’t meant exactly the opposite and so, she’d shuffled across into the passenger’s seat without a fight. Despite Koschei’s manipulations and relentless demands on her time, there was something about his incessant - _justified_ \- arrogance that made her trust him, at least with driving the TARDIS..

“Fine, but please try not to kill anyone,” she said, only half-joking, “I don’t think my insurance covers murder.”

Koschei only scoffed. He didn’t need to tell her that he thought himself the far superior driver; it was implied from the smirk he threw her as he pulled away from the kerb far faster and yet far smoother than she ever would have.

“If you took the handbrake off _before_ you accelerate, you wouldn’t have to do so much maintenance on the suspension,” he said, grinning widely.

“I like doing maintenance,” she retorted and then, they were debating the capabilities of the TARDIS Type 60s against the charms of the Type 40s as fields of red grass whizzed by.

****************

Koschei turned off the main road a short while later, rolling the car gently onto a flattened patch of grass away from the passing traffic. Although they were only an hour’s drive from U.N.I.T., it was deserted in all directions and they could’ve been on a different planet.

Faced with miles of stunning red fields of knee-high grass, the view reminded the Doctor vaguely of old films from New New Earth, only those always involved teenagers kissing and she wasn’t going to fooled by Koschei’s tricks again -

“Why are we here?” She was startled by how cold she sounded and by the way Koschei stiffened beside her, so was he.

“Take my hand,” Koschei said, ignoring her question.

He held his palm out towards her and she eyed it with suspicion.

“Fine,” she said at last, reaching out to clasp his fingers in her own, “But no more games.”

“I told you. It’s not a game,” A toothy grin was all the warning she got before he was off, dragging her behind him.

Thankfully, Koschei was an appalling runner. He stumbled through the red grass at a speed that was closer to a messy skip than a smooth sprint and the Doctor ambled after, confused until -

At the sight of a clearing in the distance, the Doctor’s own faltering steps turned into long strides and then, spurred on by a sudden fizzle of adventure and delight, she started running through the long swathes of red grass, dragging a laughing Koschei behind her.

By the time they reached the patch of younger grass, barely tall enough to reach their ankles, Koschei was panting heavily and the Doctor was beaming at the expanse of open field before them. The TARDIS was a small, blue dot behind them.

“Come here,” Koschei rasped, throwing himself down besides some bright purple wildflowers

He was looking up at her expectantly through long lashes but even his obvious, inappropriate attempt at flirtation wasn’t enough to kill the Doctor’s buzz. She’d forgotten how much she loved exploring new places, and this was more beautiful than most.

Grinning widely, she plonked herself down beside Koschei, leaving an inoffensive metre of space between them, and turned to gaze at the mass of bright, wild red.

“It reminds me of my father's land back home,” Koschei was quiet under the birdsong, “Pastures of red grass, stretching far across the slopes of Mount Perdition. I used to run across those fields all day, calling up at the sky.”

“Calling up to aliens?” joked the Doctor weakly. Koschei’s shifts in mood no longer surprised her, but his sudden melancholic tone was unsettling.

At first, he didn’t reply, only stared at her with strangely unfocused eyes and then, he was scowling at the wildflowers by his feet.

“Calling up to an empty cosmos. One that scarcely bears thinking about," he said at last.

It took a moment for the Doctor to catch up.

“You were on your own,” her eyes widened with sympathy, “As a child, I mean.”

Koschei scoffed, plucking the petals off a wildflower one by one, “Yes. Not that you'd call it childhood. More a life of duty.”

She understood completely. Gallifrey could be stifling at the best of times and for a boy like Koschei, the Oakdown name would be both a blessing and a curse.

“Why are we here?” This time, her tone was kind and genuinely curious.

Koschei took his time to answer, carefully rolling up the cuffs of his navy shirt sleeves before replying, “I want to know about the Archangel Network.”

“How’ve you heard about that?” the Doctor gaped, “You shouldn’t even know its name.”

Only a select few knew that the Archangel Network had even existed, let alone that the Doctor had worked on it. Clearly Lord and Lady Oakdown were better connected than she’d realised.

“And yet I do, so tell me what you did,” Koschei’s eyes were alight with a gleam she recognised from when she’d caught him setting off fireworks from the rooftop. It was a look that made her pulse quicken.

“Why do you care?” she replied, parrying for time, “It was four years ago.”

“I want to know,” he said, turning towards her with a hiss.

Koschei had probably been aiming for threatening but he landed somewhere between petulant and whiny and up close, his scowl was more like a pout. Pressing down on a sudden urge to giggle, knowing he’d only be furious, Doctor flopped backwards onto the grass, mulling Koschei’s request over.

She was proud of her involvement taking down the Archangel Network. It’d been a tough year that she hadn’t been able to talk about, thanks to the reams of confidentiality agreements she’d had to sign. Technically, she wouldn’t be breaking them if Koschei already knew what had happened, more or less. A few extra details couldn’t hurt.

“What do you want to know?” she said at last.

“Everything,” He grinned, settling down beside her, far closer than could be called appropriate, but leaving just enough space between them that it didn’t seem worth spoiling the peace over.

“I s’pose you know the basics? It was a satellite system developed by Toclafane Industries,” she said, glancing sideways. Koschei’s smile was so bright that it was hard to look at directly. She turned her eyes towards the blue skies above them.

“It was the brainchild of Harold Saxon,” Koschei said, “A genius.”

“A lunatic,” snorted the Doctor, “Not that I actually met him.”

“Saxon was a visionary. He connected fifteen satellites all around the world,” Koschei insisted, “It was the planet’s first 4G mobile network, binding the whole human race together.”

“That’s what Saxon wanted us to think,” the Doctor said, “He convinced every government in the world to sign up.”

“Even New New Earth,” giggled Koschei.

“Yes, even New New Earth,” she nodded, amused by his fixation on a country he claimed to hate.

“But it was shut down after a year. You shut it down,” He was laying on his side, head propped up on one arm and gazing at her with open fascination.

It would’ve been disturbing if she hadn’t already realised that Koschei really was very smart and very geeky. That part of O hadn’t been a lie.

“I had to,” the Doctor said, “It wasn’t just a phone network. Saxon was broadcasting a second signal hidden inside the first. It scrambled messages, added extra zeroes to transactions, leaked passwords, confused identities. It was chaos and it was really very clever.”

“Was it?” Koschei asked, eyes sparkling with interest.

“His signal was hiding in plain sight and it almost impossible to defeat,” the Doctor frowned up at the sky, “It was Martha Jones who worked it out. She went to every government on the planet but no-one would listen. Saxon had fooled them all.”

“Yes, but how did you bring down the Archangel Network?” Koschei said impatiently.

“Martha needed someone to hack into the network. She came to me and I disrupted the second signal,” the Doctor explained, “But I couldn’t just shut it down. Saxon was too clever for that so I replaced his signal with my own.”

She glanced at Koschei. He was staring at her, unblinking and silent.

“It took a whole year to integrate my code with its matrices,” the Doctor recalled, “It wasn’t easy. He knew I was there but he didn’t know what I was doing. Whoever Harold Saxon was, he was a madman but he was brilliant.”

“Brilliant,” Koschei echoed, face contorting into a bewildering mixture of annoyance and something that looked unnervingly like delight.

“Yes, he was brilliant,” she said, grasping for something respectable that a teacher would say, “But good always prevails and in the end, I won.”

She grinned at Koschei, expecting awe and maybe more questions, but he only scowled.

“I was distracted,” he spat, “Lucy was no help and Martha Jones kept trying to break into my office. It was going fine until you interfered.”

The Doctor squinted at Koschei, more than a little confused. Surely he wasn’t saying what it sounded like he was saying.

“You can’t be Harold Saxon,” she said, “You were thirteen years old.”

“Thirteen and the _half_ ,” he said, with the fervour of someone who was still at an age where halves mattered more than the morality of catfishing an entire planet.

“No, you can’t be,” the Doctor insisted, “You were on the Valiant. With Lucy,”

“Yes, in my office. With Lucy,” Koschei snapped, before a mischievous grin spread across his face, “So you’ve looked me up.”

If she wasn’t so flummoxed, the Doctor would probably have been more concerned that she could now tell what Koschei was thinking from how many teeth he smiled with. He was definitely flattered.

“I’m flattered,” he grinned.

“Of course you are,” she rolled her eyes, “But even if it’s true-“

Koschei interrupted, “I can honestly say every word is true.”

“- why would you do it? All that work? What was the point?” She gesticulated wildly at the sky. She’d spent so many long, frustrating nights pouring through Saxon’s code.

“Chaos, destruction, carnage. The finer things in life,” Koschei said airily, “And because I could.”

His glibness stunned her. It seemed impossible to believe that a thirteen-and-the- _half_ year old had really built the Archangel Network, that the teenager next to her had sent the entire world’s financial system into a slow, chaotic meltdown that had almost brought the Japan to its knees... and yet, she believed him, which meant that -

“I spent a year of my life in a cyber fight with an imaginary enemy and it was you all along,” she said hollowly.

“Yes, it very much was,” Koschei eyed her warily, “Are you going to tell anyone that Saxon was me? I got away with it and I’d like it to stay that way.”

It was such a childish plea for her silence that the Doctor didn’t reply at first and then, frowning up at the clouds, it hit her; Koschei hadn’t kissed her to blackmail her. He’d only wanted to get close enough to find out why his teenaged takeover had failed.

He _had_ been using her but not for anything as sinister as she’d imagined. She let out a tiny sigh of relief but before she could say anything or wonder why her stomach was suddenly a heavy sinking pit inside her, Koschei had closed the distance between them. The length of his legs pressed against hers, his chest was a warm line along her side and he was peering down at her anxiously.

“What’s wrong?” Koschei’s brown eyes were wide with worry.

“I’m fine,” she said curtly and then, another horrifying realisation hit her and she was rolling away before he could see the guilt crashing over her face.

Koschei hadn’t been tricking her; she’d simply assumed he had been up to something devious because everyone expected it of him. Even worse, he’d known about her for years and somewhere between admiring her and meeting her, he’d developed a crush. Which meant, worst of all, that she _really_ shouldn’t have kissed him, that she’d taken advantage and -

“You don’t like me now that you know you’re better than me,” Koschei snarled.

His face was a dark, stormy shadow above her. The worry was gone from his eyes and now, only rage remained.

“I didn’t say that. Why are you saying that?” She blinked up at him. Her crushing guilt was now catapulting into confusion and bewilderment.

“You think I’m lesser. I can see it your eyes,” he hissed, sitting up beside her, drawing his legs up to his chest.

His sudden anger was frightening but strangely, she wasn’t frightened _of_ him, only _for_ him. His hands were drumming an agitated rhythm on his knees - _one two three four, one two three four, one two three four -_ and his mouth was twisted into an ugly sneer.

“You think you’re so special, so different,” Koschei spat, voice was thick and his eyes darted over her face, frantic and furious.

“You’re wrong,” the Doctor spluttered, sitting up and staring at him with rising alarm. Her guilt had faded entirely, in the face of Koschei’s sudden hateful anguish.

“Now you think you’re so much more than me, and you don’t -“ he broke off, shakily, and the Doctor’s heart twisted hopelessly at the sight of his eyes glistening, as if the wrong word from her might break him.

He was so fragile; behind all that arrogance and brilliance was a boy overwrought with rage and pain and she kept making it worse. She was meant to be helping him but he wasn’t listening, wasn’t giving her a chance and then, to her mounting horror, Koschei moved as if to stand and with panic pulsing through her, the Doctor lurched forward and -

She kissed him.

And then, she was pulling him frantically back down onto the grass, scrambling to shrink the space between them, wrapping her arms around his shaking frame. She pressed a flurry of frantic kisses to his jaw, his cheeks, his mouth. If only she could break through the fog of his blinding rage, if only he could see what she really thought of him, how she really saw him.

“You’re wrong,” she said, planting sloppy, desperate kisses against Koschei’s mouth, “None of that is the truth.”

His lips were a tight, closed line against her own but he wasn’t pulling away. He only lay there, stiff and cold beside her. His stillness frightened her. She wanted him happy, gazing up at a purple sky alight with fireworks. She wanted him gleeful, speeding down the motorway while she shrieked beside him. She wanted him good, because he was so clever and so capable and she knew she could help him, if only he would let her.

“You're a genius. You're absolutely brilliant, you really are,” She breathed into the crook of his neck, clutching him against her, “And you could be so much more. Let me help you.”

His silence was unbearable and finally, when her heart was about to burst from fear and she thought she might actually cry, Koschei rasped, “What about Harold Saxon?”

“Forget him. That’s the past,” She pressed another shaky kiss against his mouth, “ _You're_ my responsibility from now on. The only Koschei Oakdown in existence.”

And then, Koschei was softening beside her, his arms curling in a tight circle around her neck and then, finally, he was kissing her back.

When they’d kissed before, the Doctor had been in a daze, floating along in the fog of gentle warmth. This time was entirely different. Now, there was an intensity thrumming through her, her limbs flailing to pull him closer, tongue pressing urgently into his mouth as she tugged him over her. It was only when he was lying on top of her, his body a solid, steady weight on hers that the thick, unbearable fear started to ease.

After that, she was only conscious of Koschei’s wide, shining eyes and his mouth descending to meet hers again and again. He was a confident kisser now. They’d spent enough time practicing, but more than that, his tongue nudging softly against hers felt familiar and comforting and from the way he melted into her, he felt the same.

She didn’t stop him when his hands drifted down to play with the hem of her t-shirt. When his fingers brushed against her bare skin, she only sighed and kissed him harder, and then, when he pulled her t-shirt upwards, she only lifted her arms up to help him. It was only her bra that broke them apart.

“It’s easier when you’re the one wearing it,” Koschei mumbled, obviously embarrassed by his own fumbling.

“You mean when you were Missy?” She said, reaching backwards to unhook the clasp herself.

He nodded but before she could ask anything more, her bra was tumbling off and he was pressing her back into the grass.

Even though the Doctor was the one laying exposed in the open air of a grassy field, it was Koschei who was suddenly shy. His hands grazed awkwardly at her sides, and he only glanced down once, briefly, before pressing his mouth against hers in a hurried kiss.

The Doctor only sighed, shivering beneath him. Her nipples were rubbing against Koschei’s shirt and as much as she wanted to feel his bare skin, she shouldn’t. She wouldn’t. She closed her eyes, counting the shirt buttons pressing into her - _one two three four, one two three four, one two three four_ \- and wrapping her arms around his shoulders, arched up against him, with a quiet moan.

And then, with curiosity finally overtaking him, Koschei’s hands shifted to palm at her breasts before he ducked downwards. The sight of him, wide-eyed and mouthing tentatively at her nipples had the Doctor trembling all over. The sun was beginning to set and she should’ve been chilly but instead, her body was thrumming with heat, as Koschei grew more confident, licking and sucking and even biting at her nipples until she was panting and squirming beneath him.

It was only when Koschei toyed indecisively with the waistband of her trousers that the Doctor stilled in sudden wavering horror. His fingers danced nervously from her belly button to her hip and then, they were drifting upwards to tweak idly at her nipples, and he was kissing her again.

She sighed into his mouth, mostly with relief. Koschei was her student, she was his teacher and still, she couldn't have said for sure that she’d have stopped him if he’d wanted to go further. She only knew she wouldn’t have wanted to stop him, and that was something she couldn’t think about. Not now, not when she was still kissing him, mesmerised by how his eyes were so dilated and how softly his eyelashes fluttered against her cheek when he planted kisses from her mouth down along her neck..

How could he have ever thought that she didn’t like him, when she liked _everything_ about him, far far more than she should? She liked his cleverness and his brilliance and even his wild, chaotic unpredictability. She liked the way his trembling hands clutched curiously at her breasts and the weight of his body pressing down on hers. Most of all, she liked how she could feel every inch of him against her, including the ones she really shouldn’t.

His erection was a long, hard line between them, even through the fabric of his chequered purple trousers. The urge to feel his bare skin against her own - to wrap her hand around his cock - was overwhelming, but still, she resisted, twisting her fingers into the back of his shirt instead. They had to stop somewhere and this was far enough. It was already too far, but still, she was arching up against him, rolling her hips into the heat of his cock against her, mouthing wetly at his neck. They would stop soon. She would stop it soon but for now, they could - 

Koschei suddenly stiffened, his eyes growing comically wider than she’d ever seen them, his mouth falling open against hers. Time slowed and the world narrowed, and the Doctor watched helplessly as panic and then pleasure swept across Koschei's face, his hips stuttering roughly against hers as the rush of orgasm rumbled through him. It was the most incredible, most horrifying, more captivating experience of her entire life.

Finally, Koschei stilled, staring down at her with something like panic or fear or shame in his eyes. The Doctor stared back, shellshocked but before she could speak, Koschei had scrambled off her and then, before she could stop him, he was gone.

**Notes for the Chapter:**

> I'd love love love to know what you're thinking and feeling!! And any other thoughts if you want to share because there's a lot going on in this chapter.
> 
> My original plan was that they were going to have a heart-to-heart about what being Missy was like, but then you all were so suspicious in your lovely comments of Koschei's motives for kissing the Doctor that I figured it was time to reveal SOMETHING!
> 
> This fic is largely unplanned so any speculation goes far 😂


	7. Chapter 7

**Notes for the Chapter:**

> So... it's been a whole month since Koschei came in his boxers... Whoops!
> 
> I was almost ready to post this two weeks ago but I got really ill. What I thought was winter flu turned out to be the new mutant covid... so I really hope you enjoy this chapter - I spent most of the last two weeks wishing I was well enough to be posting it. But for the longest time, I couldn't even open my eyes.
> 
> Anyway, a reminder: The Doctor and Koschei were making out in a field. Koschei got a little overexcited and then took off... here we go!

By the time the Doctor had scrambled to her feet, tugging her bra and t-shirt back on in a fumbling mess of limbs, Koschei was a fading purple dot in the distance. By the time she reached the TARDIS, he’d disappeared entirely.

The rest of the evening passed in a frantic blur. The Doctor drove for miles in all directions, circling back on herself again and again with increasing desperation. For someone who had spent the past week making it impossible for her to ignore him, the young Master had a startling ability to vanish off the face of the planet when he wanted to.

It was long past midnight when the Doctor finally turned back towards U.N.I.T., rationalising that Koschei would have made it to the school on foot hours ago. In any case, he had famously run away twice before, long before she’d met him. He was resourceful and inventive and he wasn’t a child.

But he wasn’t an adult either. Koschei was still only seventeen and wasn’t running off an entirely childish thing to do? Guilt and worry and yet more guilt were solidifying into sickening stones in the Doctor’s stomach. She’d tried to help him and she’d only made it worse. Somehow, when it came to Koschei Oakdown, she only ever seemed to make it worse.

Parking the TARDIS in her usual spot was an unpleasantly surreal experience. It felt like entire lifetimes had passed since Koschei had been lounging on the garage workbench, unwilling to give her even a moment of peace and now, the Doctor would have done anything to have him goading her again.

If only she could turn back time, she would go back to when they’d been kissing in the field. She’d stop herself at the moment before she’d rocked her hips up against his erection, before Koschei - brilliant, unpredictable, _underage_ Koschei had -

The Doctor slammed the TARDIS door shut with a grunt and strode across the U.N.I.T. grounds towards the boys’ accommodation block. It was late; Koschei _had_ to have come back on his own and with any luck, she’d be able to spot him through his bedroom window and convince him to come down so they could talk...

But there was nothing to differentiate one set of drawn curtains from the next, she had no idea which room was Koschei’s and she didn’t know whether the students slept in dormitories or alone. The Doctor stared up at the blacked out windows with a sinking heart. She would have to wait until morning before she could speak to Koschei and hopefully, he’d be willing to stick around long enough to listen.

*************

The Doctor was the first one through the refectory doors when the canteen girl Bill opened up for breakfast. She’d already eaten four Gorvian doughnuts and was halfway through a bowl of mice crispies by the time the Brigadier joined her.

“Where is everyone? It’s already 8am,” the Doctor grumbled unreasonably. Only a handful of students had made it down to breakfast and none of them were Koschei.

“If they’re not playing hyperball or practising dakaro, they’re still asleep,” answered the Brigadier, “I’ll round them up during the morning patrol. But more importantly, how was your road trip? You were late back last night.”

The Brigadier poured himself a bowl of mice crispies, unaware of the Doctor’s mouth freezing mid-chew.

“The TARDIS broke down,“ she mumbled at last. If the Brigadier had heard her returning, he might’ve seen her arriving without Koschei, and then what would she say?

But the Brigadier only laughed, “I suppose Master Oakdown didn’t react well.”

The Doctor’s spoon landed in her cereal bowl with a loud clunk, “How’d you know that? Did you see him?”

“No, but I know what he’s like, Doctor,” the Brigadier said, “And I can’t tell you how glad I am that he’s _your_ problem now.”

“So you haven’t see him,” the Doctor said, heart sinking.

The Brigadier shrugged, “It’s Saturday. I won’t see most of the students until Monday morning.”

“So you don’t know where he is?” She pressed. She’d convinced herself that Koschei had come back the night before, but dread was growing in her stomach once again.

“Presumably he’s still in bed, considering how late you got in. I’m surprised _you’re_ up, to be honest,” the Brigadier glanced at her curiously.

For a moment, the Doctor considered coming clean. At the very least, she could say that Koschei hadn’t wanted to wait for her and had taken off before she could stop him. That was technically the truth, minus one or two details... but then, the Brigadier was rising to his feet.

“Why don’t you join me on the morning patrol?” he asked, “You can drag Master Oakdown out of bed yourself.”

***************

Koschei wasn’t in his bedroom. Unsurprisingly, the door was locked but the Brigadier’s heat scanner confirmed that there was no-one inside.

“Sometimes they try to sneak a few more hours sleep but nothing gets past me,” the Brigadier said, tapping on the glass screen proudly, “Master Oakdown must be up to no good already.”

The rest of their patrol passed without any sign of Koschei but in the bright morning light, the urge to confess to the headmaster had passed. It was obvious from the stream of students crossing the school gate that the older ones were free to come and go as they pleased on the weekends, and hadn’t the Brigadier told her himself that he was leaving her in charge of Koschei? She’d caused the problem so she should be the one to fix it; She only had to find him and persuade him to come back.

The Doctor started by digging up Koschei’s phone number from his student record on the school’s computer system. She had access because she was his teacher; a fact she didn’t want to think about but also couldn’t _stop_ thinking about. She rung him intermittently but his phone remained switched off and she didn’t dare leave a message. After that, she drove back to the town they’d been to yesterday and even all the way to the red fields. There was no sign of Koschei anywhere.

Sunday passed the same way and soon, her determination had faded into despair. Foggy with sleep deprivation and with an exhausting cycle of guilt, worry and more guilt grinding away at her, the Doctor had rung Koschei’s phone far too many times, walked every corner of the U.N.I.T. grounds and was now numb with distress.

Every time she heard a low laugh or a distant bang, she’d leap upwards, hoping to see Koschei bouncing with glee over an explosion of some kind, but it never was, and by dinner on Sunday - which Koschei didn’t attend - the Doctor had replayed the entire encounter in her mind a thousand times.

They’d been talking and then he’d been upset. She’d kissed him, and she shouldn’t have but it wasn’t the first time or even the second, and it’d been _nice_. Too nice and then Koschei had lost control, which wasn’t that surprising in hindsight, but had certainly shocked them both.

Had he been embarrassed by it? Or had he been frightened or angry? Koschei was infamous for his short fuse after all, and if he _had_ been angry, was it because she’d kissed him or was it because it’d gone further than he’d wanted it to? Than _she’d_ meant for it to.

Or had he left because he’d thought _she_ was angry at _him_? She’d frozen in horror and maybe he’d misread her shock for disgust. The possibilities were infinite, only one person knew what had really happened and he wasn’t _here_. His absence was making her guilt turn into desperation, and soon she was making promises to a seventeen year old boy who wasn’t around to hear them.

If he came back, she’d never kiss him again and would only help him to be good. If he came back, she would give him everything he wanted, even if she shouldn’t. If he came back, she could ask him what had gone wrong and then she could fix it. She’d fix everything, if only she could speak to him. And then it hit her.

It was easy enough to make a sparkler. It was harder to make one that was five metres tall and would burn brightly enough to be seen for miles around... but not impossible. She climbed the teachers’ block like Koschei had done only a few nights before and just like he had, she waited until midnight exactly to set it alight.

For the whole hour that it burned, she sat, eyes roving in all directions, imagining Koschei’s steps on the gravel or the front gate squeaking. But there was nothing. Finally, the sparkler died out with a sad, defeated hiss and the Doctor was left out of ideas and utterly alone.

By the time she’d stumbled back to her flat, she’d made up her mind. First thing in the morning, she’d tell the Brigadier everything. He would call the Judoon Police and she might even end up in Stormcage Prison, but at least they’d know that Koschei was missing, and maybe they would find him. He’d be mortified and she’d never see him again, but it was a small price to pay if she knew he was safe.

And then, she saw him. The lamp on her bedside table cast a warm glow over her bed where Koschei lay sleeping. His clothes - the same ones from Friday - were folded neatly on the back of a chair like a tidy nightmare, waiting for her to come home.

The vision of him was so unexpected and so utterly yearned for that the Doctor could only stare unblinkingly for a long, breathless moment... and then he was waking up, squinting at her in the dim light and tugging on her wrist until she was tumbling into the bed beside him.

Seconds later, Koschei’s arm was draped around her waist, his chest pressed against her and the duvet was snug around the both of them. He was naked except for his boxers - in her quiet hysteria, she wondered momentarily if he’d washed them in a sink or fetched a new pair from his bedroom - and then his legs were tangling up between hers, his nose nuzzling sleepily into the crook of her neck and she breathed a long sigh of relief. He was back.

“How are you here?” She whispered wondrously into his bare skin.

“I saw you were looking for me,” Koschei murmured, two days of teenage stubble scraping against her cheek.

If the thin fabric of her own pyjamas hadn’t been between them, she might have recoiled from the heat of his body against her, but surging relief was making her giddy. He was back, he was safe and he was in her bed.

Her brain stuttered over that last thought, tripping over it even as she wound her own arms around him. He was safe in her bed. He was safe. He was in her bed. They would be two separate thoughts.

“You disappeared,” she whispered at last, “I thought you were dead.”

Koschei frowned, blinking at her sleepily, “Why would I be dead? I disappeared. It’s what I do.”

She knew that. She’d read enough about him to know that, and he’d told her so himself. There’d been plenty of stories that the Gallifreyan tabloids didn’t know about and he’d even bragged about the horrible ones, like when he’d run away to the Cheetah Valley Sanctuary and taunted one of the big cats from the side of the enclosure until it'd bitten him.

She’d been about to rebuke him for it - torturing animals was low, even for juvenile delinquents - but then he’d said “cheetahs hunt in twos” with such strange longing that she hadn’t said anything at all. He’d also told her that the cheetah’s teeth had left a scar beneath his collarbone - and now, even in the dimness of the lamp light, she could see the mark on his bare skin, amidst the smattering of chest hair between his nipples.

He was practically naked in her bed and she should look away or send him to his own room. At the very least, she should insist he borrow a t-shirt... but the thought of doing anything that might push him away frightened her. He’d only just come back and she couldn’t cope with adding another night’s sleep deprivation to her exhausted mind and body.

This time, she was the one rolling over him, hooking her legs between his and dropping her head onto his shoulder. Soon, she’d practically pinned him to her bed beneath her. He'd have to push her off him if he wanted to leave... but he only draped his arms around her, hugging her tightly against his bare chest.

“I couldn’t find you,“ she said into the space between his nipples, “I spent all weekend looking for you. There was no sign.”

Koschei only hummed, as if disinterested and suddenly, her relief at his reappearance began to morph into anger.

“Why did you leave?” the Doctor asked sharply.

He was quiet for a long moment, “I was angry.”

And just like that, her guilt was flooding back. He’d been angry. He’d been angry at her because she’d let it go too far. He hadn’t been ready for what had happened. It was all her fault.

“I’m so sorry,” she said, her voice cracking with misery and Koschei blinked at her in confusion before burying his nose into her hair.

“No, I was angry at me,” he mumbled, “I don’t want you think I’m a kid.”

“You _are_ a kid,” She could hear the distress in her own voice. It was a fact she couldn't refute and surely, he understood that.

“I’m eighteen in a few months,” Koschei said stubbornly.

“And I’m still your teacher until the end of the year,” the Doctor was fighting back the sudden urge to cry.

“You can quit tomorrow and then you won’t be,” he said and she stilled.

She hadn’t thought of that. That now Koschei was back, she could simply quit. She could tell the Brigadier he’d have to find someone else to teach her classes and anyway, Koschei Oakdown wasn’t that much of a lunatic, from what she’d seen. Absolutely chaotic and volatile but not exactly dangerous. She could leave tomorrow and never look back, never see or think about him again.

“If you leave, I’ll have to follow you,” Koschei said casually, as if he could read her mind.

“What? No,” she frowned, thrown off kilter by his certainty, “What about your exams? Cosmic Science at the Academy?”

He snorted, “I’ll blow things up until you come back and stop me.”

The Doctor sat up in horror. Koschei was grinning toothfully at her, a bright wild menace threatening her from her own pillow.

“You promised me no more explosions,” she said.

“Then you can’t run away,” he said, “Not without me.”

“You ran too,” she pointed out reasonably.

“No, I disappeared. That’s different,” Koschei paused, “And I came back.”

And he had come back, which was all the Doctor had wanted. She’d spent the last two days imagining what would happen if he hadn’t, played out what she’d tell the Brigadier, wondered how she’d face Lord and Lady Oakdown. Worst of all, she’d wondered whether she’d broken him when she’d meant to help him.

She lay back down on his chest, shivering. The relief that he was back was still pounding through her and despite his outlandish threats, she couldn’t stop her hands drifting over his bare skin. He was real, he was safe and he was in her bed.

“I won’t run away,” she said at last, “As long as you don’t make anything explode.”

Koschei didn’t reply at first but then he was burying his nose into her hair again, his arms wrapping around her shoulders in a tight embrace. The heat of his skin made her tingle in a way that reminded her of the reason he’d run off in the first place.

She hesitated but she needed to say it, “And it’s natural what happened in the field.”

She didn’t need to be more specific. Koschei knew what she meant; she could tell from the way his chest went from slack to steel beneath her. She barrelled onwards, hoping to quell whatever feelings were raging through him before he could bolt again.

“You’re young,” She avoided insisting that he was a kid again, although that was more for her benefit than his, “It’s always like that the first few times. It takes a while to learn how to control it.”

The Doctor trailed off. She hadn’t actually asked if it had been his first time being close to someone in that way. It was obvious enough that it was and she didn’t want to embarrass him any further.

“I liked the massive sparkler. It was very dramatic. You can teach me tomorrow,” Koschei said at last.

“Teach you how to make a sparkler?” she asked sleepily. For the first time since she’d come to U.N.I.T., she finally felt like she might get a decent night's rest.

“Teach me everything. Show a bad boy how it's done,“ Koschei hummed, and then his hand drifted down to squeeze the curve of her hip before settling on the small of her back.

The Doctor didn’t reply. Instead, she pressed her nose into the crook of his neck and tried to concentrate on the only thought that really mattered; Koschei Oakdown was safe in her bed.

**Notes for the Chapter:**

> So yea, feeling pretty fragile and self-pitying after my covid adventure so if you have time to hit kudos or comment, it'd be like regeneration energy to this worn-out soul.


	8. Chapter 8

**Notes for the Chapter:**

> E for Explicit! But the intimacy is both emotional as well as physical here so prepare for a lot of chatter in-between the sex.
> 
> Why? Because I like playing with twisting canon into human... and I have plot seeds to plant.

Koschei had disappeared by the time the Doctor woke up. She would’ve thought she’d dreamt him out of desperation and worry, only the smell of smoke and burning embers still lingered over her sheets. It was a scent so familiar and so reassuringly _Koschei_ that she clung gratefully to the pillow he’d slept on for a whole ten minutes, wondering idly where he’d gone this time.

Thankfully, she only had to wait an hour before she saw him again. Her heart somersaulted wildly at the sight of him in her classroom, sprawled besides Miss Osgood and waiting for their A-Level Chemistry class to start. His hair was damp and tousled, he was clearly fresh from a shower and in his hand was the homework the Doctor had set the class last week.

She skim-read all three pages of his essay on stereoscopic isomers over her lunch break. A very tiny part of her worried it would be a detailed account of all the ways she’d taken advantage of him, or a list of demands he now intended to blackmail her for, but it was only a perfectly written essay, well-researched and completely deserving of an A grade - even if it felt wrong to mark him so highly when she could perfectly remember the tickle of his chest hair against her cheek and his arms slung around her back.

Concentrating on anything that wasn’t Koschei became even more of a struggle during her afternoon Physics class. After spending a week fixating on his presence, the weekend worrying about his absence and then a whole night clinging to him in her bed, it was almost impossible to resist glancing over at him every other second.

Koschei was being far more discreet, neither paying her any more attention than usual, nor avoiding her gaze. Instead, he seemed intent on taking apart Miss Osgood’s scientific calculator and although the Doctor knew she should be glad he was behaving exactly like his usual bratty self, his apparent disinterest was agonising. Especially when class finally ended and Koschei left without a backwards glance.

The Doctor spent the rest of the day marking the other students’ essays and reminding herself that Koschei had classes that she didn’t teach, that he knew where she was if he wanted to find her, and most of all, that she was his teacher and she shouldn’t be chasing after a seventeen year old student. Not now that he was back safe on the school grounds anyway.

And then, to the Doctor’s overwhelming relief, Koschei arrived promptly at her flat for what technically should’ve been his fifth evening of detention. This time, they didn’t waste a single moment pretending. He’d barely waltzed through her front door before they were tumbling onto her bed, clothes flying off in a whirlwind of purple and blue around them.

She should’ve stopped him, should’ve sat him down and had a serious conversation about it all... but she didn’t have the heart to refuse him. She never had and she especially didn’t now; not when she was stripped down to her bra and knickers, Koschei’s boxers were on her bedroom floor and his bare skin was a burning heat against her own. She shouldn’t be looking and she definitely shouldn’t be touching, but she was starting to lose track of what rules she’d decided she was willing to break.

“Give us a kiss,” Koschei said, practically vibrating against her, “And say something nice.”

“You win,” the Doctor replied, her voice cracking helplessly and then, she was falling into him, pressing him into her bed and kissing him until she couldn’t breathe.

This time, Koschei lasted long enough for her to wrap her hand around him. His long lashes fluttered and his chest heaved, as he gazed up at her in wonder. His mouth made pretty noises as she stroked and squeezed. It was hypnotic, he was beautiful and she never wanted the moment to end. Too soon, his cock was jerking in her hand, his cum spilling over her fist and something unbearably soft filled his eyes.

“Doctor,” Koschei murmured thickly but before he could say another word, she’d silenced him with another deep kiss.

The sight of him, wide-eyed and sticky beneath her, was the most captivating thing she’d ever had the privilege of seeing. It was both incredible and utterly damning; they had gone too far and she needed to put a stop to it before they went even further.

But it seemed that Koschei had the very opposite in mind. Even as she kissed him softly, she could feel his hands fumbling impatiently with the clasp of her bra.

“It’s definitely easier when I’m the one wearing it,” he mumbled against her lips.

The Doctor nodded in delirious agreement and then paused, blinking down at him. She needed time to think, to find it within herself to draw a line somewhere that wasn’t entirely terrible, and conversation seemed like an ideal way to distract her brain from the rush of arousal coursing through her body.

“Tell me what it was like,” she said, “When you were Miss Oakdown.”

“What do you want to know?” Koschei asked.

He’d managed to unhook her bra, but his hands only drifted over the curve of her bare back, his urgency fading. He seemed to like talking to her as much as he liked touching her.

The Doctor thought carefully before answering. It was a good question. She’d already seen photos in the Gallifreyan tabloids of Victorian corsets and striking black eyeliner, and the Brigadier had also explained that Koschei had arrived at U.N.I.T. aged fifteen as Miss Oakdown. It had now been roughly six months since Koschei had returned for the school’s summer term as the raging young Master.

“Was it difficult?” the Doctor asked at last, “Being her?”

Koschei shook his head immediately, “I used to burn like the sun, like a whole screaming world on fire. And then I was Missy and it was bananas.”

The Doctor blinked at him, confused, “Is that good bananas or bad bananas?”

“I considered it an upgrade,” he grinned, “And the Brigadier’s not as old-fashioned as he pretends to be. I shared a room with Osgood. We had girls nights and I painted her nails.”

“So that’s why you’re friends. Sort of,” the Doctor realised.

She had wondered why Miss Osgood looked more resigned than nervous around Koschei, unlike the other students who tended to give him a wide berth.

He shrugged, “She’s much more useful to me that way. She said so when I moved in and it seemed like a good point, well-made. But enough about Osgood, you’re in bed with _me_.”

The Doctor winced. She didn’t need the reminder. Not when his cum was drying between them and his sweat was cooling on her skin.

“What about now?” She gestured vaguely, “Are you who you want to be?”

Koschei hummed at the ceiling for a long moment before he answered.

“I loved being Missy. Every second of it. But I’m someone else now,” he paused before snarling suddenly, “And if you say it was a phase, I’ll scratch your eyes out.”

Despite Koschei’s unexpected viciousness, the Doctor only stared at him, thoughtfully. It’d been exactly eight days since they’d first met and he’d been pretending to be O for three of them. She hardly knew Koschei and yet, she could already see through the outlandish threats to the scared boy beneath.

“I’ve never felt particularly one way or another. I’ve never thought about it. I suppose I never had to,” she said softly, “But it doesn’t make a difference to me if you’re Miss Oakdown-”

“Missy,” he corrected her sharply.

“It doesn’t make a difference to me if you’re Missy or Master Oakdown,” the Doctor continued, “Or if you’re O or Harold Saxon or Koschei. I think you’re brilliant. All of you. I really do.”

It wasn’t the first time she’d told him that but she could tell it still pleased him from the way he grinned wolfishly at her, all big eyes and teeth, before he flipped her onto her back and began kissing his way down her body.

When Koschei’s hands finally paused questioningly on the band of her knickers, his gaze bright and curious, the Doctor only stared back at him. And when he started easing them downwards, inch by slow inch, she still didn’t say a word, only raising her hips upwards in burning silence.

And then her knees were parting, her thighs falling open and Koschei was nestling himself between them, staring down at her naked body with unabashed curiosity. It was a long, breathless moment for them both before he reached out to brush a dry finger against her labia.

“Lick it first,” the Doctor winced and then, she was suppressing a laugh as Koschei’s tongue poked out obligingly, “I meant, lick your finger or you could do this.”

Shakily, she reached for his hand and slowly lowered it to where she was already wet with arousal. Instantly, Koschei’s eyes widened almost impossibly large and he froze, slack-jawed and transfixed.

Breathing deeply, willing herself patient, Doctor watched him carefully, wondering what he’d do next, but Koschei only circled the tips of his fingers around her entrance thoughtfully.

Belatedly, she realised there was something she should have asked him much, much earlier, “What do you know about sex?”

“Only the theory of it. The mechanics,” Koschei replied, still peering closely at her labia, “The girls classes were all about not getting pregnant. It was boring so I made the plastic babies explode. It was _carnage_.”

He dissolved into a flood of giggles as the Doctor grimaced, but before she could reply, Koschei continued.

“You’re too old to get pregnant, right?” he asked.

“What?” she glared, mouth falling open in shock, “Exactly how old do you think I am?”

“Ancient, obviously,” he said, “But I like it.”

She scowled. In reality, she wasn’t _that_ much older than him, power dynamic and authority issues aside. She was about to explain exactly how old she _wasn’t_ when -

“I did watch some holo-porn,” Koschei blurted out.

The Doctor froze, her indignation suddenly forgotten, “Holo-porn? How did you...?”

She trailed off. U.N.I.T. almost certainly blocked access to ‘adult holograms’ but Koschei was certainly more than capable of breaking through any restrictions on the network.

“ _When_ did you...?” she asked instead.

“In the Matrix,” he said, “I was there all weekend. I was just playing, I got lost in there and then I thought, I could do some research.”

“Research,” the Doctor echoed hollowly.

The Chamber of the Matrix was the repository of all Gallifreyan knowledge. It was both a physical library and a virtual data bank, holding every book, video and hologram ever made. Including ones that were definitely off-limits to anyone underage.

“And what exactly did you see?” the Doctor asked nervously.

In some ways, holo-porn was very realistic - the holograms were so detailed and lifelike, you could mistake the figures for being in the room with you - but in other ways, they were ludicrous to the point of terrifying. Especially for someone like Koschei who was inexperienced enough not to know any better.

“I found the complete set of Fornication Times,” He glanced up at her uncertainly through long lashes, “But I only watched one. There was a woman who had someone’s whole hand inside her.”

The Doctor exhaled sharply in relief. That wasn’t too bad, all things considered and it certainly explained why he was tapping out a nervous beat on her thighs.

“Those holo-porns tend to go from zero to hundred, and skip all the numbers in-between,” She wrapped her fingers around his gently, “We can start with one. If you want to, I mean. I like one.”

And then, between Koschei slowly sliding a single finger into her and the way his eyes widened in wonder, words escaped her. Her head fell back onto her pillow as she sighed with relief.

“Two?” Koschei asked, a few minutes later.

The Doctor nodded, still wordless. Half her brain was in teacher mode, still wanting to explain that he shouldn’t believe everything he saw in holo-porn. The other half didn’t trust herself to speak, lest she ask for more before he was ready.

“How does that feel?” Koschei was gazing her curiously, his two fingers bending and stretching inside her.

“Brilliant,” the Doctor said, and then figuring he would probably appreciate notes, she added, “Curl your fingers up towards-“

She broke off with a deep, strangled moan, causing Koschei to freeze in wide-eyed shock.

“That’s it,” she panted reassuringly, “That’s the Gallifreyan Spot. First discovered by an unknown Gallifreyan scientist in the 5th Century and much disputed by Earthlings to this day. And very, very good.”

There was a long pause while Koschei stared at her and then his fingers were pumping slowly, pressing against the bundle of nerves inside her in a precise, steady rhythm.

“Interesting,” he said, a moment later.

The Doctor only whimpered. From the way Koschei’s eyes were darting from her face to his fingers inside her and back again, it was clear that it wasn’t her rambling history lesson he found so fascinating.

And then, to her quiet horror, his tongue was poking out again and Koschei began licking at her tentatively. He had no sense of technique or any awareness of her clitoris but somehow, the sensation of his tongue swiping curiously between her labia was the single, most arousing thing the Doctor had ever experienced.

She dropped her head back onto the pillow with a quiet moan, revelling in Koschei’s experimental licks and sucks, while his fingers still curled rhythmically inside her. She’d have to show him where her clitoris was next time, because this was already a lot for him to discover in one day - and before she could panic over whether that passing thought meant she’d already committed to a ‘next time’ - Koschei put his whole mouth over her vulva.

The sudden, overwhelming wet heat was glorious. The Doctor groaned, clenching hotly around his fingers and then, in a move that was so fleeting that there was no way it was intentional, the tip of Koschei’s tongue brushed over her clit.

Suddenly, she was surging upwards, her hips rolling urgently against his mouth. It was exactly like the first time that Koschei had kissed her, when she had kissed him back instinctively; only this time, instinct had her grinding her clit against his tongue, her fingers curled so tightly in his hair that he couldn’t have pulled away if he tried.

Between the glorious heat of Koschei's mouth, his eyes so awestruck and helpless, and the rough pressure of his tongue as she rocked upwards, thighs clamped around his head, undulating with growing desperation, it wasn't long before the Doctor was moaning in loud relief as wave after wave of hot pleasure crashed through her.

For a few, long moments, the only sound was the Doctor’s exhausted gasps echoing around the bedroom and the thumping of her own racing heartbeat in her chest. It was only when the fog of her orgasm started to fade that she realised with horror exactly how tightly she was gripping Koschei's hair.

His mouth was swollen and shiny and his eyes were glistening as he blinked up at her, shell-shocked. But before she could panic or apologise - before guilt could sweep away the pleasure humming through her - Koschei was crawling up the bed towards her, a broad grin spreading across the face.

“That was spectacular,” he was so obviously pleased with himself that the Doctor couldn’t bring herself to do anything but nod.

And then he was kissing her sweetly and she could taste herself on his tongue. The sheer wonder of it - of Koschei’s enthusiasm and joy - was astounding, and a glowing sense of something she couldn't pinpoint had her reaching out to tug him closer and tighter until he was in her arms. But as good as he felt on top her, he also felt clammy against her bare skin, and with a jolt, she realised his erection was softening against her stomach. The Doctor glanced down, confused, until -

There was a wet patch at the foot of her bed. Koschei had at some point come again and if it had been anything like the first time, out in the red grassy fields, he hadn’t been able to help himself. Thankfully, he didn’t seem inclined to flee this time. Instead, he was pulling the duvet over them both and she was letting him, even though she should really send him to sleep in his own room, lest this become a habit.

The Doctor took a deep breath, about to say something, only Koschei’s arm was already curling possessively around her waist. One more night wouldn’t hurt, she thought, before the rhythm of his heartbeat against her cheek lulled her into sleep.

**Notes for the Chapter:**

> I admit it's a little restrained of the Master NOT to watch all the holo-porn in The Fornication Times with utter delight, but this is Koschei and he's still a baby-Master.
> 
> Please leave kudos/comments if you can and... any requests as to what Koschei should get to try next?
> 
> Happy New Year!


	9. Chapter 9

**Notes for the Chapter:**

> Hey hey, it's my birthday! So here's a new chapter and the overall chapter count has leapt up once again. Oops!

Once again, Koschei was gone by the time the Doctor woke up, and although his absence should’ve filled her with relief, it only gave her space to fall back into guilt. After all, sneaking out early only meant that Koschei knew he shouldn’t be staying over in the first place - he was pushing at boundaries and as his teacher, she had a duty of care she was failing to uphold.

Without any classes to teach that day, the Doctor spent the rest of her morning pacing restlessly around the flat, unable to stop replaying the night before and all the things she should’ve done and said when Koschei had appeared to her door - how she could have turned him away instead of kissing him, how his eyes had dilated as she held the weight of his cock in her hand, how hot and keen his tongue had been between her -

The front door slammed as the Doctor stormed out of her flat in a sudden whirlwind. Since she couldn’t shut her brain up, she was going to do what she always did when she needed a distraction - spend the day working on her TARDIS. Unfortunately, while the complexities of servicing her car’s exitonic circuitry could keep the Doctor’s mind away from Koschei, it didn’t stop the boy himself from showing up only half an hour later.

“You missed lunch,” Koschei said, dropping a paper bag down by the Doctor’s toolkit.

She glanced over at him warily from underneath the TARDIS hood. Despite all her brooding, she hadn’t considered that Koschei would double down on his attentions, but in hindsight, it was blindingly obvious. He’d kept turning up unannounced before and now it would be even harder to keep him away. But she didn’t have a choice. She’d taken too many firsts from him and this is where it had to stop, even if the sight of his long lashes blinking at her inevitably made her falter.

“Thanks,” the Doctor mumbled at last, “But I’m not that hungry at the minute.”

“You will be later,” Koschei replied and then he was settling himself on the workbench beside the TARDIS, “I’ve got a double free period now and I’m going to spend it here.”

The Doctor only nodded and turned back towards the engine. She didn’t trust herself to speak. She wasn’t exactly sure yet _how_ she was going to put a stop to whatever was going on between them, and until she figured it out, she didn’t want to say anything that would cause more damage than she was trying to prevent. Koschei had already proven himself prone to fits of dramatics when he was hurt or angry and she didn’t need any more midnight fireworks or weekend manhunts.

Lost in thought, several minutes passed before the Doctor realised that there was a distinct lack of noise emanating from the workbench. Slowly, she looked round with a creeping sense of dread; silence and the infamous Master Oakdown couldn’t be a good thing. But Koschei had only fallen asleep, curled up on his side and shivering a little, despite the fancy waistcoat he was wearing and the relative warmth of the garage.

The Doctor hesitated for a short second and then she was wriggling out of her long, grey coat and draping it gently over him. When she picked up her screwdriver again, she was careful to keep the noise to a minimum. It wasn’t that she cared about Koschei’s well-being _specifically_ ; it was simply that she always looked out for her students, sleep was important for a teenager’s healthy development and she was also _somewhat_ culpable if he was a little sleep-deprived.

It was a thought that led the Doctor back to her main concern; how to distance herself from Koschei in such a way that he was neither hurt nor enraged by her rejection. The first and most crucial thing to do, she decided, would be to limit the time spent alone with him, until he had lost interest or found someone his own age. It shouldn’t be too hard. They’d only met nine days ago and teenagers were notoriously fickle with their affections.

Next and just as importantly, she needed to put some thought into how exactly she would help him to be good. Koschei’s delinquent behaviour was the very reason why the Brigadier had called her to U.N.I.T. and she still hadn’t yet done anything about it. That was yet another failure on her part; even if they _did_ carry on doing what they were doing - which they weren’t going to - kissing didn’t exactly help Koschei with whatever attention-seeking, rage problems he had... Although, deep down, the Doctor was starting to suspect it was only boredom and loneliness at the root of Koschei’s chaos, and nothing more sinister than that. Which meant that technically, an inappropriate _something_ with his teacher _did_ help -

It was a stupid thought and she shouldn’t be having it. She would’ve slammed the TARDIS hood down in frustration, only doing so would’ve woken Koschei who was still sound asleep behind her.

The Doctor tinkered with the TARDIS environmental gauges for another two hours, pondering how she’d get through their last two detentions. She needed to put distance between them, and prevent any more repeats of the night before, without arousing his suspicions - or anything _else_ of his. Just as she was contemplating whether or not faking a cold would keep Koschei from kissing her, an unexpected form of help arrived.

“There you are,” the Brigadier peered around the garage door, smiling jovially, “I can’t let you out of my sight, can I, Doctor?”

She blinked at him through her goggles, “Can’t you?”

“You run off when I do! I haven’t seen you since Saturday, when you were looking for Master Oakdown,” the Brigadier said, “It seems you found him.”

He cast a puzzled look at Koschei, whose messy black hair and purple socks were poking out from both ends of the blanket that was the Doctor’s coat.

The Doctor didn’t reply. Lending out a coat to a student wasn’t technically inappropriate and it was pretty much the only thing she’d done with Koschei that wasn’t, so it was best to say nothing at all.

“I have a favour to ask,” the Brigadier said, “Tonight is Master Oakdown’s sixth detention with you. Could you bear to have a couple more?”

“Detentions?” asked the Doctor, worried.

She was already struggling to see how she’d get through the next last two evenings alone with him. Any more seemed impossible.

“A couple more students,” clarified the Brigadier, “Have you met Mr. Pink?”

The Doctor thought for a moment. She hadn’t spoken to any of the teachers since she’d started but she had seen their names on the patrol rota and passed a few in the refectory at meal times. Wasn’t Danny Pink the one with the posture that screamed ex-army? The kind of guy who looked like-

“He teaches P.E.!” she said, grinning triumphantly.

“He teaches Maths,” the Brigadier ignored the way the Doctor’s eyebrows rose sceptically, “And he has two students who have been neglecting their homework requirements.”

She could see where this was going, and it was even better than anything she could’ve planned. Firstly, she could tell that Koschei was awake and listening. She couldn’t tell _how_ she knew exactly, considering he was lying perfectly still and his breathing was slow and even... but she knew.

“You want me to have them for detention tonight,” the Doctor said, her tone purposefully bland.

“And tomorrow. Mr Pink has some prior engagements,” the Brigadier said, “And since you’re supervising detention anyway...”

Agreeing would mean no more evenings alone with Koschei and since he was witness to the fact that it literally wasn’t her decision, he was unlikely to react with another midnight fireworks show.

“I don’t really have a say, do I?” the Doctor said. There was no harm in over-egging it a little.

The Brigadier only laughed, “They’ll be outside your classroom at 7pm.”

He then turned towards the workbench and tugged on her coat, revealing a wide-awake, scowling Koschei.

“Come along, Master Oakdown. Your free periods are for studying, not napping,” the Brigadier said, “Nardole’s making a fresh pot of coffee. If you’re lucky, we’ll get there before he adds the teabags.”

**************

Koschei didn’t return from wherever the Brigadier had taken him, not that the Doctor had been expecting him to. She was just curious. She spent another hour tinkering with her TARDIS before her stomach rumbled and she finally remembered the packed lunch Koschei had brought her earlier. It turned out to be three custard cream Grovian doughnuts from the school refectory, which she gobbled down with delight before realising that the silence of the garage now felt empty and misery inducing. The fact that her coat now smelt like smoke and burning embers only made her feel even more hollow.

But if there was one thing the Doctor was good at, it was ignoring her feelings. She managed to add a few bespoke improvements to the TARDIS navigation systems, tune into no less than three Earth radio stations, _and_ polish all the roundels by the time she had to head to her classroom. Koschei was already waiting outside, throwing dark looks at two tiny Year Seven students beside him, who were clutching their Maths textbooks tightly to their chests.

“Hiya,” the Doctor grinned at them all brightly but only Koschei nodded back, his expression cold and impassive. The other two appeared to be frozen in fear.

The Doctor suppressed the urge to roll her eyes. To her knowledge, Koschei hadn’t blown anything up or threatened to throw anyone off the language block since term had started, and since these two were only in their second week of their first year at U.N.I.T., he was obviously trading on his reputation alone.

Thinking quickly, the Doctor flicked through the younger students’ workbooks. A quick glance at their incomplete homework was enough to reveal the problem. Neither of them had understood the concept. They hadn’t been skiving; they’d simply been lost.

“Master Oakdown,” she said carefully,

She wanted him busy and distracted this evening, so that he wouldn’t realise she was trying to distance herself from him. And it wouldn’t hurt if the quaking 11-year-olds saw a slightly softer side of Koschei.

His dark eyes narrowed at her with suspicion, “Yes, Doctor?”

“Do you know how to solve quadratic equations?” she asked.

As expected, Koschei scoffed, “Of course.”

“Teaching someone else how to solve them is a whole different skillset,” she said.

He rolled his eyes at her. He knew perfectly well he was being played but-

“Sit,” he snapped at the Year Sevens, “And if I have to repeat myself, I’ll cut your ears off.”

Even though the Year Sevens were now trembling even _more_ , the Doctor couldn’t help the grin spreading across her face. It got even wider when the corner of Koschei’s lips quirked in a tiny smile back.

Detention passed quickly after that. She’d managed to plan three more Chemistry experiments while Koschei monologued at surprisingly detailed length on the quadratic equation and all its uses. She only realised it was already 9pm when Mr Pink knocked on the classroom door, wanting to check that his students had behaved and that the Doctor was happy to supervise detention again tomorrow. It was rambling and a little unnecessary, but she let him linger. After all, it meant Koschei had no choice but to leave with the younger two, even if a small part of her wanted him to stay.

***********

The Doctor jolted awake, blinking into the darkness. Something was different; not wrong, just strange. She stared at glowing numbers of her clock. It was midnight exactly and there was a dim light glowing from beyond her bedroom door.

There was someone in her flat but somehow, she wasn’t afraid. Even before she turned the corner into the living room, she knew what she’d find; Koschei, demanding, relentless and sitting exactly where he shouldn’t be, with no regard for the rules.

And there he was, hunched over a pile of books like someone frantically cramming for a morning exam. Beside him was a brown leather notebook. It was the same one she’d seen him writing in when he’d been pretending to be O, only this time she could see that it was more a mass of arrows and jumbled letters than anything that looked like regular Gallifreyan.

Distantly, she knew she should be concerned or even angry that he’d broken in _again_ , but strangely, it was comforting to see him there. She’d clearly spent so much time worrying about what trouble he was causing when he was out-of-sight that seeing him doing something harmless filled her with relief. It was the only logical explanation for the swell of warmth she felt at the sight of him.

“What are you doing?” the Doctor asked, blinking at him dimly.

Koschei only smiled at her, “I couldn’t sleep.”

She picked up one of his books. It was a treatise on the political history of Gallifrey that he had borrowed from the Matrix library. Clearly, her A-Level classes weren’t challenging enough for him if he had this much time on his hands.

“I let you nap too long this afternoon,” she said, “You’ve ruined your sleeping pattern.”

“You’re not my mother. Unless you want to be,” Koschei burst out laughing as she recoiled in horror, “I thought not.”

“Why can’t you read in your own room?” she said, hating the flush she could feel spreading across her cheeks.

“Nardole patrols after lights out. He’d spot my lamp,” he paused, “And I like it here.”

The Doctor considered him carefully for a moment. Despite Koschei’s claims of wakefulness, there were dark rings under his eyes and even his hair seemed to have lost its bounce.

She wavered. If she went back to bed and left him out here, it’d be giving him what he wanted without hurting him. It was the careful, kind distance she’d promised herself she’d put between them.... but he was already here, it was only one more night and he really should be sleeping. And it was utterly pointless even thinking about it anymore, when her hand was already reaching out to pry the pencil from his grasp

And then, for the third night in a row, Koschei was in her bed wearing only his boxers. But this time was different; this time he was sitting up against the headboard with his book in hand, reading by the dim light of her bedside lamp. The Doctor laid down on the other side of the mattress, leaving a precisely-calculated distance between them. Not that it mattered as Koschei only shifted over until her cheek was soft against his hip. Soon, his fingers were curling in her hair, massaging soft, soothing circles into her scalp. She let him, and then she was drifting into a warm sleep.

When the Doctor woke a little later, Koschei was still reading, his book casting a shadow over her face, and she was nuzzling into something warm that was somehow making her mouth water. It took her a long, lazy moment to realise what exactly she was pressing her nose into and why the air smelled so good. She froze, and then, too tired to pull away - or simply too dazed to care - she turned to gaze up at him.

Koschei looked even more exhausted than before. And maybe it was her sleepy, uninhibited brain that wanted him to put the book down, maybe it was how sweetly he was smiling down at her or maybe it was just how tempting the shape of his half-hard cock was against her cheek but, without a second thought, she was mouthing wetly at him through the thin fabric of his boxers.

There was a dull thunk as his book slipped out of his hand onto the bedroom floor, and then the only sounds were Koschei’s breath catching as she lapped at his cock. Soon, he was rock hard, the front of his boxers soaked with saliva and pre-cum and somehow, he smelt even _more_ delicious.

Logically, the Doctor knew it was only pheromones that was making her feel that way, but knowing the literal biochemistry of _why_ didn’t change how intoxicating it felt to bury her nose into him, her hands tugging on his waistband until his cock sprang free from his boxers and -

She paused, staring at the bead of white glistening on the tip of his erection. As much as she wanted to lick, taste, suck every inch of him... she paused, glancing up at Koschei’s face. He looked absolutely wrecked and she hadn’t even touched him properly yet. And in that moment, more than ever, she wanted to see what he’d look like when she did.

Slowly, with her eyes fixed on his, she leant forward, hovering for a long, questioning second over his erection. Koschei had stopped blinking. He might even have stopped breathing and then finally, _finally_ her pursed lips were descending and his eyes were widening in perfect, mesmerising delight.

As overwhelming as it must have been for Koschei, the Doctor could feel her own heart thumping erratically as if it were also _her_ first time. She stilled, only halfway down his cock, her tongue a soft, unmoving pressure against his sensitive skin. The sensation of him in her mouth - hot, hard, _perfect_ \- was one she wanted to savour.

This was the side of Koschei no-one else saw. The maniac who was gentle, brushing her hair back with shaking hands even as he stared at her with hungry, heated eyes. The master manipulator who was so sweet, naked and stripped bare of his carefully-crafted outfits and disguises. The genius who behaved like he would conquer the world on a whim, only now he was pliant in her bed.

It was so confusing. How could she help him be good when she kept blurring the lines between them? Why couldn’t she stay away? And then, as her tongue curled underneath his foreskin, his eyes somehow grew _even wider_ and the Doctor knew exactly why she couldn't stay away. Exactly why she didn't _want_ to.

From the way Koschei was now panting heavily, he wouldn’t last long, which was arguably a good thing. It was already past one o’clock and they both had A-Level Physics in the morning. It just meant that she only had a few precious minutes to memorise the feel of him against her lips, the way his breath caught as she wriggled her tongue and then the whimper he made when she hollowed her cheeks and started to suck.

At first, she kept her movements light and slow, revelling in the heat and weight of him in her mouth, before pulling off to trace the point of her tongue along a vein. He was trembling beneath her and he was _beautiful._ After that, she was drawing large, wet, looping circles over, under and around, and then, sensing he was close, she mouthed wetly at the head of his cock, sucking hard, working her tongue quickly until Koschei stiffened with a groan and she was rewarded with a flood of salty, _delicious_ heat.

Afterwards, he was utterly boneless, which made it easy for her to tug him downwards until he was a soft lump on the pillow beside her.

“Wow,” Koschei mumbled, gazing at her through heavy eyelids. Sleep was finally catching up with him.

Instead of replying, the Doctor pressed a shaky kiss against his jaw. It was as if he had gifted her a bomb and instead of running away, she’d decided to throw herself on top of it and hold it close.

*******

Wednesday’s classes passed smoothly. Koschei had already solved all the calculations on the Physics worksheet before she’d finished explaining the equations the class would need, so she pretended to not to see him reading his library books while she taught the rest of the class.

He wasn’t given the same leeway in Chemistry. The students had three titrations to do for their A-Level coursework that year and even Koschei couldn’t skip the paperwork. Thankfully, he didn’t make a fuss when she discreetly confiscated his book, so she turned another blind eye to the fact that Miss Osgood was all doing most of the fetching and carrying for their experiment.

She returned the book later that evening, when he arrived for his final detention. The two Year Sevens were back, far less terrified of Koschei than the day before, judging by how excitedly they were waving yesterday’s Maths homework, now with big A grades emblazoned across on them. Koschei only clutched his library book and stared at her beseechingly as if he didn’t know how to respond to students smiling at him instead of quaking.

Amused, and feeling rather pleased with herself - despite how badly she’d messed up with distancing herself from Koschei the night before - she let him hide in the corner with his book while the Year Sevens were set to work washing all the glassware in the Chemistry cupboards. Once again, detention passed quickly and the Doctor only realised it was 9pm when Mr Pink knocked again.

This time, he was holding a small, white patisserie box, “A little something to say thank you for covering for me.”

“Oooo, a meringue spaceship,” the Doctor grinned, delighted.

“You really helped me tonight,” Mr Pink said, “And yesterday.”

Out of the corner of her eye, she could see Koschei lingering, making a show of packing his books away at the slowest possible pace but Mr Pink only waited politely until she’d dismissed all three students and was locking the classroom door behind them.

“I’ll walk with you,” Mr Pink said, with a bounce in his step, “My flat’s on the floor above yours.”

It was a short walk but it was difficult to follow his conversation when Koschei was mere metres ahead of them, his back ramrod straight.

“Have you met her?” Mr Pink said. His tone implied it wasn’t the first time he’d asked her the question.

“Sorry, met who?” the Doctor blinked. She thought he'd been talking about his dinner date at The Meringue Galaxy.

“Clara Oswald, my girlfriend,” he said, “She’s one of the English teachers. She’s the one with the big eyes.”

The Doctor tried to picture her but the only eyes she could see were Koschei’s, glinting at them out of the darkness, even as he turned away toward the students’ accommodation.

“Can’t say I have,” she mumbled.

Koschei didn’t look back again. He didn't show up at her flat or in her bed later either. It was exactly what the Doctor had wanted, so why - when she woke up alone as she always did - did she suddenly feel so bereft?

**Notes for the Chapter:**

> Since I'm spending my birthday in lockdown and I live alone, now's a good time to leave me a comment if you haven't before 😊
> 
> To celebrate, I thought I'd do a birthday game. Whomever can most accurately guess what Koschei is going to do Mr Pink in the next chapter will get a gift fic written by me, with prompt, plot or kink of their choice!
> 
> I've already written the next chapter and the game is open until I post it... Feel free to make as many guesses as you want and I promise it is definitely guessable!
> 
> hint 1: I love twisting canon into something that works in this AU world  
> hint 2: Koschei promised the Doctor 'no explosions'  
> hint 3: this picture is how the next chapter begins:
> 
> hint 4: ....big big big hint...


	10. Chapter 10

**Notes for the Chapter:**

> Hello! Firstly, I hope there's still people out there wanting to read this fic. Sorry it's been a while. I got a new job! It's super and I love it but it's a step-up so I ended up spending all my free time triple-checking my work cos I'm anxious like that. I'm hoping I chill out as I settle in...
> 
> Secondly, does anyone remember where we left off? Probably not, so a reminder, Koschei had his last detention, Mr Pink turned up to walk the Doctor back to her flat, and when she wakes up, she realises Koschei hadn’t snuck in for once...

Every secondary school in Gallifrey was more or less the same. While some had deeper pockets and better facilities, staffroom politics and exam pressure never changed... but U.N.I.T. was still unfamiliar territory for the Doctor. She was less than two weeks into her first term, had yet to meet most of her colleagues, and even her flat, one of many identical apartments in the teachers’ block, still felt more like a hotel suite than a home.

And yet, three nights of Koschei in her bed - so few and yet, far too many - were all it took for the Doctor to feel the sharp, desolating lack of him when suddenly, he wasn’t. She’d tumbled out of bed twice that night, rolling towards a warmth that wasn’t there, and when she woke shortly after sunrise, her nose buried in a pillow that no longer smelled like smoke and burning embers, it took a long, painful minute to remember that Koschei’s absence was a good thing.

After all, the previous evening had been their last detention together, which meant no more late hours spent in the close confines of her flat together. And since Koschei hadn’t appeared in her bed - uninvited or otherwise - then perhaps his interest in her had already waned. That would only make it easier to distance herself from him, and if she _had_ gotten used to his presence far too quickly, she’d just as soon adjust to his absence.

And there was, admittedly, one unexpected benefit to the whole inappropriate mess; the time spent together had given her some much needed insight into the young Master and she now had a plan for how to help him be good. It was even one that the Brigadier was bound to approve of.

It was obvious that Koschei Oakdown wasn’t a ‘King of Evil’ at heart, however much he claimed to be. He was simply - literally - far too bright and far too bored for his own good, and while U.N.I.T. couldn’t hold his interest, the Doctor was certain she knew what would; Cosmic Science at the Academy. She’d find the first year reading list, dig up her old textbooks and Koschei could get a head start on his undergraduate degree before he’d even finished his A-Levels.

The best thing was, she wouldn’t even need to tutor him. He was smart enough to teach himself and in any case, the whole point was to keep him occupied while maintaining her distance. Of course, it meant he’d be bored at the Academy, but by then he’d be someone else’s problem and she’d be far, far away from whatever chaos he might wreak.

The Doctor was starting to feel a little less miserable by the time she started walking over to the Science block. Not because Koschei would be in her Chemistry class in half an hour, but because it was beginning to feel like she could finally focus on helping him be good. And then she heard it - a loud, insistent beeping, followed by a sudden blare of sirens and finally, the sound that every teacher dreaded: the thunderous roar of teenagers stampeding.

Without a second thought, the Doctor was running across the school grounds, her heart thumping in horror. At best, a fight had broken out and she had to tear some scrapping twelve-year-olds apart. At worst, Koschei had blown something up. It would certainly explain where he’d been all night, since he hadn’t been with her and while it was a stupid, reckless thought, she’d rather he _had_ been with her, if the alternative was that he’d exploded a building instead.

The Doctor skidded to a halt outside the Mathematics block. Thankfully, it still looked intact, and while the fire alarms were blaring at an excruciating volume, there was no sign of smoke nor flames. Instead, the sprinkler system was running at maximum capacity, judging by how soaked and bedraggled the U.N.I.T. students looked as they fled from the two storey building.

She circled round to the front entrance quickly. Some teachers she didn’t recognise were herding the wailing teenagers in the direction of the playing fields, which probably meant they doubled as the official fire assembly point. Everything was loud and frantic but ultimately, it didn’t look like anyone was in particular need of her help, and so, the Doctor turned back towards the Mathematics block curiously.

Every public building in Gallifrey was fitted with state-of-the-art, life-prolonging CyberMaintenance technology. False alarms never happened and actual emergencies were rare and contained quickly. If the artificial intelligence had deemed the situation dire enough to start one of the 3W sprinkler programmes - water, wet foam or wet chemicals - and on such scale, then there must’ve been a fire big enough to put the whole building at risk.

She scanned the classroom windows with interest. It was difficult to see through the thick curtain of what was either water or wet chemicals pouring from the ceiling, but it looked like most of the students were now out of the building. She glanced over to the front door and at the last few stragglers stumbling out, and all the sudden, the entire world seemed to have fallen silent because instead of sirens and wailing students, the only sound she could hear was -

“Hi,” Koschei mouthed, his fingers wiggling in the air as he waved at her from the front doorstep.

He was the last in a long line of students evacuating from the building and despite the lack of explosions, it was startlingly obvious that he was the mastermind behind the mess. It wasn’t the drama or the disruption that gave Koschei away; it was the fact that he was the only one holding a large, black umbrella.

While everyone else looked like drowned rats, Koschei looked immaculate. He’d curled his fringe and it looked like he’d even applied eyeliner for the occasion. And then, he was sidling up to her with his umbrella held high above their heads.

It was a ridiculously obvious ploy to squeeze himself against her. There weren’t any sprinklers _outdoors_ and the Doctor would’ve shoved him away if she didn’t think it would cause a scene. More of a scene.

She turned towards him, scowling, “What have you done?”

“Oh, stop looking all cross-pants,” Koschei was clearly delighted with himself, “I'm giving you a gift.”

She gaped at him. They were the last words she’d expected him to say. She’d thought he’d lost interest or grown bored of her. She’d assumed he’d had his fun and didn’t want to go any further. She’d even wondered if it _had_ been just a game to him all along. She hadn’t considered for a single second that he might’ve had something else in mind.

“What gift?” she asked at last, already dreading his reply.

Koschei’s smile was all teeth, “He won’t be bothering you anymore.”

“ _Who_ won’t be bothering me anymore?” The Doctor could feel the first twinges of a headache beginning deep within her skull. It was almost certainly due to Koschei’s exasperating riddles and not the alarms that were still blaring around them.

Instead of replying, Koschei only grinned even more maniacally and jerked his chin at the windows behind them.

"What?" she said blankly, and then she spotted it.

One of the classrooms had completely disintegrated. Where rows of desks and chairs had once sat, there were now only misshapen lumps of plastic on the floor. But - she glanced quickly through the other windows - whatever had damaged that classroom hadn’t affected any of the others. She turned back towards Koschei, confused.

“Oh, come on, Doctor, catch up,” He was bouncing with excitement now, and as his glee grew more palpable, so did her fear.

She looked back at the ruined classroom. Although the furniture was a collection of molten puddles on the floor, it didn’t look like there’d been a fire. There were no scorch marks, no plumes of smoke and no sign that anything had been set alight. Instead, the chairs looked less like they’d gone up in flames and more like they’d been melted down by some kind of -

“Acid,” the Doctor gasped, eyes flying up towards the sprinklers as Koschei giggled wildly beside her.

But it still didn’t make sense. Whatever emergency programme the 3W system had decided to run, it would be something that wasn’t corrosive. Something that was safe for humans -

The Doctor swung round towards the last few, shrieking students beside them. To her relief, none of them looked like they were fussing because they were drenched in acid rain. Instead, they were simply egging on Mr Pink, as he pulled on what looked like one of the CyberMaintenance hazmat suits.

“What? Why is he...?” She trailed off, confused once again.

“That’s Pink’s classroom,” Koschei nodded at the disintegrated mess inside.

“Okay,” the Doctor said slowly, still not understanding.

She watched as the Maths teacher, now encased inside the silver protective outfit, marched into the building. It was surely a move that was contrary to U.N.I.T.’s evacuation policy, unless he knew something she didn’t... but then he placed two gloved hands over the largest sprinkler inside his classroom. Mr Pink was trying to hold back the acid rain by sheer force alone.

“He’s so stupid,” Koschei scoffed, disdain pouring off him in waves.

The Doctor sighed. She could hardly disagree, but she still didn’t understand what the Maths teacher had done to deserve this mess in the first place. She was about to question Koschei further when suddenly, she realised something else alarming. He had shifted even closer to her.

“Tiny bit pleased?” Koschei murmured softly, his gaze flicking down to her lips, “Oh, go on, crack a smile.”

Thankfully, he’d also dipped the umbrella lower, hiding them both from view, and finally, now that she was looking directly into the bright, possessive glint in his eyes, she realised why he’d done it.

“All of this, just to warn someone off?” the Doctor said, “Because he was being _nice_?”

“He’s a nanobrain,” Koschei only rolled his eyes, “If you must have a pet, I can introduce you to Ms Oswald. She’s perfect.”

“She’s dating Mr Pink,” she snapped, gesturing behind Koschei, “Look, I expect they come as a set.”

Ms Oswald had indeed arrived sometime in the last few minutes and was trying to help Mr Pink. Clearly the brighter of the two, she was ordering the remaining gawping students to search around the building for anything that looked like a safety valve. And her eyes were almost as big as Koschei’s.

The Doctor glanced sideways at the teenager, “Why do you like her anyway?”

“She’s a control freak and I can relate,” he said flippantly.

It was a strange reason to like someone, and at any other moment, the Doctor might even have asked him why he’d liked _her_ but there were more pressing things to think about.

“You don’t get to pick my friends,” she said, finally feeling her shock starting to bubble into anger, “Or hurt people I talk to _once_.”

“Twice,” Koschei said, “And he brought you dessert.”

“I’m not going to run off with someone because they bring me sugar,” she said sharply, trying not to remember about how stupidly thoughtful she’d found it when Koschei had brought her custard cream doughnuts only two days earlier.

“You can’t run off with anyone who isn’t me,” he snarled suddenly, “You promised.”

“I’m not running off with _anyone_ ,” she snarled right back, “But you promised no explosions-“

“Ta-dah!” Koschei gestured wildly around them, his umbrella twirling in the air.

“You know what I meant,” the Doctor snapped, “You don’t get to hurt people when you don’t like something.”

Koschei’s expression was hardening into a cold sneer but she barrelled on, a sudden fury overwhelming her. She hadn’t slept well, she’d missed him far more she should’ve and yet, seeing him again had only made her feel worse. How could she ever have liked him when he kept _choosing_ to be bad?

“Fine, let’s have this out, once and for all,” she said, “You have to stop all this, you _have_ to be good. Not because it’s fun and not because it’s easy. Because it’s right.”

She knew she sounded desperate and she was definitely yelling but this was important. He _had_ to hear this.

“You have to be good,” she repeated, shouting over the wail of the alarms, “Because it’s right, because it’s decent and above all, it's kind. And I know what you’re capable of. I _know_ you can be a good person.”

But Koschei was only staring at her flatly, “See this face? This is the face that didn’t listen to a word you just said.”

And then he was spinning on his heel.

“No! No!” the Doctor yelled after him, “When I say no, you turn back around!”

But Koschei didn’t stop.

*****************

This time, the Doctor didn’t do a single thing about Koschei going missing. After all, disappearing was what he did. He’d told her so himself after the first time, so there was no point worrying about him _now_. In any case, he was seventeen. He was practically an adult and he could look after himself.

The only thing she did do was stay silent. When a team of CyberMaintenance technicians arrived later that day to recalibrate the entire 3W system, the Doctor only watched while they puzzled over the code scrambling their sprinkler programmes. Since no-one seemed to suspect any deliberate wrongdoing, there was no point letting them know that Koschei was to blame. The Brigadier would only punish him with more detentions and she’d be the one stuck with supervising him. It was best to say nothing at all.

Then, when Koschei didn’t show up for classes the next morning, the Doctor merely breezed through her lessons as if his empty chair meant nothing. And if the bio-scanners didn’t flag his absence to the Brigadier, that wasn’t her problem; the school register shouldn’t be so vulnerable to hackers that a teenage boy could play truant whenever he was in a sulk.

Whether Koschei was ‘practically an adult’ or only ‘a sulking teen’ largely depended on what the Doctor was thinking about at any given minute. Taking his anger and jealousy out on Mr Pink was both immature and impetuous, and yet if his acid rain had actually hurt someone, the Gallifreyan High Council would have surely tried him as an adult in the criminal courts. Especially with the track record he _already_ had.

There was also the matter of how Koschei had walked away from her. After everything that had happened between them, it was his right to leave if he’d wanted to, but she was still his teacher and he should have stayed and listened. He was beyond her discipline and she only had herself to blame.

And then, to the Doctor’s surprise, Koschei was waiting for her in her flat after dinner that evening. And although a part of her was relieved to see him so soon - he’d only been gone for a day and a half this time - the sight of him, sullen and scowling on her sofa, only rankled. She didn’t want to argue with him and yet -

“Why are you like this? When will you stop?” she said sharply, as if there’d been no interruption to their fight.

“Never. You don’t control me, Doctor,” Koschei’s eyes were dark, “I don’t obey anyone.”

“I don’t want you to obey me,” she snapped, exasperated, “I just want a little less chaos.”

But Koschei only tilted his head at her thoughtfully, “No, you don’t. Not really.”

Startled and more than a little flustered, the Doctor didn’t reply. He was infuriating and worst of all, he might even be right. After all, no-one had ever captured her attention the way Koschei had - no-one had ever _behaved_ the way he did - and while she hadn’t spent the last thirty six hours looking for him, she’d still spent most of the time pointedly trying _not_ to think about him.

Finally, she slumped down on the sofa beside him. She was tired of fighting, it wasn’t getting her anywhere and at least the feeling of fear and worry that tended to swell when Koschei wasn’t around had abated a little. If he was here, he wasn’t doing something catastrophic somewhere else. Unless he’d already done it.

“Where were you this time?” she asked, glancing at him carefully,

“In the Matrix,” he said readily, “Same as last time.”

“Watching more holo-porn?” she said a little snidely. Misery and exhaustion were making her mean.

“No. I was reading. And I got more books,” Koschei’s eyes were suddenly big and wobbly and even though she knew full well that he was a master manipulator, the Doctor couldn’t help but feel a little guilty.

She didn't want to be unkind about his inexperience or his curiosity, and she _especially_ didn’t want to give him a complex about anything to do with sex. She’d already done enough damage in that department.

“I’m sorry,” she said sincerely, “I didn’t mean anything by that.”

But he still looked wounded. The Doctor grimaced. Normally, she didn’t say much when awkward things like _feelings_ popped up, but Koschei had a tendency to make them unavoidable.

“I really am sorry. The acid rain scared me and I... reacted,” she said.

It wouldn’t be right to say she’d overreacted. If anything, she’d under-reacted, considering that she hadn’t told the Brigadier that Koschei was to blame, and other than pointing Miss Oswald in the direction of the sprinkler valves that morning, she hadn’t helped either.

“It wasn’t going to hurt anyone," Koschei mumbled, "I diluted the acid so it was only strong enough to sting and I dissolved the furniture beforehand. It looked worse than it was.”

“Oh,” the Doctor said, genuinely surprised, “That’s not as bad as I thought.”

“I know,” Koschei replied earnestly, “I would’ve shot him a jealous rage, but I knew you wouldn’t like it.”

The Doctor couldn’t tell if he was joking or not, but it did sound like he’d thought it through carefully. After all, the Brigadier had brought her to U.N.I.T. because Koschei had _actually_ burned down the Social Sciences block only four months ago. Presumably, he’d hacked the 3W sprinkler system that time and turned it off entirely and so, it _was_ an improvement that it was only some tables and chairs that needed replacing this time. Arguably, Koschei _had_ been good after all.

“But you still can’t go round doing that,” the Doctor said at last, “Mr Pink only brought me dessert because I covered detention for him. He got two evenings off work. It wasn’t really a fair trade.”

“So he owes you much more than a meringue spaceship,” Koschei’s eyes narrowed, “I’ll make him pay.”

She was about to howl in despair when she realised there was a playful glint in his gaze and his knee was pressing against her own. This time, he was definitely joking.

“It wasn’t that good a dessert anyway,” she said, unable to stop the smallest of smiles from escaping at the sight of him visibly softening beside her, “I prefer custard creams and you know that.”

It was hardly the most romantic declaration but Koschei seemed appeased enough to offer something back.

“I wanted your attention,” he explained, “You said I could ask but it was our last detention and then you left with Pink and didn’t say a word to me.”

The Doctor squeezed her eyes shut in silent, painful horror. Deep down, she’d known that was why he’d done it. That it hadn’t only been about a stupid dessert or the fact she’d had a conversation with someone else. It was because she’d tried to push Koschei away, hadn’t wanted another teacher to see them interacting and most of all, while it was an awful admission of guilt to think it, let alone to say it -

“I had to pretend that there’s nothing between us,” the Doctor said at last.

“So there _is_ something between us,” Koschei’s eyes were gleaming brightly, “You admit it.”

Feeling sick, she nodded, not trusting herself to speak.

“I was going to come over after,” he said, “But I was too angry.”

Shame was making her shift her gaze to the floor, but somehow the Doctor felt compelled to whisper, “I wanted you to. I missed you when you didn’t.”

There was a long silence and then -

“I’m moving in," Koschei said firmly.

“What? No,” She turned to stare at him in horror, even as her heart thudded with something that felt dangerously like excitement, “You can’t. That’s crazy.”

“If you refuse, then I’ll-,” he started.

“No,” the Doctor groaned, burying her face into her hands with a tired wail, “No explosions, no blackmail, no threats. Please, Koschei.”

“I was going to say, that if you say no, then I’ll only stay over on weekends,” he grinned, “And all the weekdays that end in Y.”

And despite everything that was wrong with the situation, the Doctor couldn’t help but laugh. He was completely insane and she never quite knew exactly when he was serious or when he playing one of his games. Except right now, she knew that he meant every word and it was precisely the moment she should stop playing along.

The Doctor sighed, pressing the tips of her fingers into tired eyes. She needed to refuse him - if only she could think of the right words to say - but before her brain could scramble something kind together, Koschei was already tugging at her wrists, pulling her hands into his own.

“Say it again,” he said, his eyes bright to the point of feverish, “One more time.”

“What?” the Doctor frowned, thinking back, “No explosions?”

“No, after all that,” he said, “Say it again.”

It took her a second to catch up, “Please, Koschei?”

“Mmm,” Koschei was grinning at her, wolfishly, “I like it when you say my name.”

The Doctor gulped. Suddenly, she couldn’t remember why she’d been so angry with him in the first place, or what she’d needed to tell him so urgently.

“Koschei,” she said again, weakly and then, he was leading her to her bedroom - _their_ bedroom - and she still wasn’t stopping him.

**Notes for the Chapter:**

> They're moving in together! Unless the Doctor says no of course. But with her track record so far.... 🤣
> 
> And on to the most important thing, congratulations to Liber (Liberalia) who wins my birthday guessing game! Your guess of "he turns on the anti-fire sprinkler system in his classroom/floods Danny's flat (possibly w/the kids' help?). The opposite of fire/explosions is flooding" was so stunningly accurate that I think my heart actually stopped when I read it. Did Koschei help you hack into my drafts?
> 
> Thank you everyone who took part. You made my lockdown birthday magical. I was laughing so much and I highly recommend you all take a look at the other guesses on the previous chapter because they were all brilliant and insane and absolutely worthy of Koschei. You're all far more imaginative than I am, I hope my version is not too dull after all that!
> 
> Also, please leave me comments cos I love to hear what you think and feel. <3


	11. Chapter 11

**Notes for the Chapter:**

> You were probably expecting smut judging by where I left off on the last chapter. Alas, the smut wouldn't come (pun intended) and so you are left with plot that will make sense later.

Undressing Koschei was like unwrapping the world’s most interesting birthday present while it was trying to unwrap you _too_. His arms crisscrossed hers, hands pulling at suspenders, fingers picking at waistcoat buttons before finally, their clothes were hanging in a neat pile off the back of a chair. It must’ve been Koschei’s doing because the only direction the Doctor had been aiming for was ‘off’, and then they were tumbling onto her bed in a mess of limbs.

Kissing Koschei was now far more familiar than it ought to be. Kissing Koschei when he was _naked_ was a completely different matter and for once, where doubt and guilt normally loomed, the Doctor only felt a rush of giddy exhilaration. Koschei had disappeared for the second time, but he’d also come back and everything seemed different now.

Even though their argument had been awful, and his behaviour had been bad to the point of dangerous, the fact that he’d returned on his own accord felt like progress. And while their fight hadn’t exactly been resolved, the revelation that the acid rain incident had essentially been harmless was practically a victory. Koschei had said - almost in the same breath - that he’d never be controlled and yet, in his own way, he _was_ trying to be good.

And then, there’d been his insistence that he’d never obey her. As his teacher - as someone trying to help him - that should’ve been frightening but instead, Koschei’s words had only filled her with a buzzing sense of relief. She had no authority over him, he would do whatever he wanted, whenever he wanted, and right now, he wanted to be here. He wanted to be in bed with _her_.

When he _wasn’_ t, it was easy to remember all the reasons she should refuse him; he was underage, he was her student, she had a duty of care. And when he _was_ \- his chest hair tickling her bare nipples, his legs tangling up with hers, his hands roving over her hips - it was even easier to kiss him until the whole world melted away and the only thing she could think about was how good it felt to have him right beside her.

And, having admitted that there _was_ something between them, all of her confusion and frenzy and worry had melted away. Instead, there was only Koschei in her bed and the sheer joy of him, wide-eyed and demanding.

“Say something nice,” he said, teeth tugging at her bottom lip.

“You win,” she said, “You win, you win, you win.”

They kissed for what felt like hours, tangled up around each other. They kissed until there was a sticky pool of pre-cum between them and her thighs were wet with arousal. They kissed and kissed and kissed until finally, the rush of adrenaline and wonder ebbed enough for the Doctor to realise that Koschei had a dazed look in his eyes that wasn’t simply because his cock was hard against her stomach.

“You’re exhausted,” she said, concern hitting her like a cold wave. It explained why his stamina seemed to have significantly improved, despite it only being a week since their disastrous afternoon in the red fields.

“No, I’m good,” Koschei mumbled stubbornly.

And even though she knew he didn’t mean ‘good’ the way she so badly wanted him to mean it, something about the way he was blinking at her so earnestly made her say -

“I know you are,” she pressed a kiss against his forehead, “I know you’re trying. But you still need rest.”

His only response was an unhappy whine, but then his eyes were fluttering shut and a moment later, he was fast asleep.

It was unsurprising really. Knowing Koschei, he’d probably been up all night reading in the Matrix library. And he almost certainly hadn’t had much sleep the night before that either; sabotaging the 3W sprinkler system and destroying Mr Pink’s classroom would have taken several hours at the very least.

The Doctor sighed, tugging the duvet over him before rolling out of the bed and reaching for her pyjamas. Koschei _was_ trying to be good, but did it count if he was doing it for the wrong reasons? By his own admission, he’d been careful not to hurt Mr Pink because he’d known it would upset her. It could almost be considered thoughtful and yet, he’d only held back for reasons that were entirely selfish; there was no way she’d let him move in if he’d actually injured someone.

Not that she was letting him move in _anyway_. The Doctor slid back into bed carefully, leaving a yawning gap between her and Koschei. The good thing about him falling asleep was that it gave her some time to think.

There were a multitude of reasons why he couldn’t move in. The first was that her flat was literally in the teachers block and it was a miracle that Koschei’s far-too-frequent visits hadn’t been noticed already.

Secondly, both the Brigadier and Nardole patrolled the school grounds with alarming enthusiasm. The headmaster only had to point his heat scanner towards Koschei’s room one night to realise that he was out of bed. How long would it take before he realised that Koschei was in _hers_?

And thirdly, they’d only known each other for twelve days, if she didn’t count the year she’d spent trying to bring down Harold Saxon’s Archangel Network. She was willing to bet Mr Pink and Ms Oswald hadn’t moved in together quite as quickly, and they were actually _in_ a relationship.

And then, even though she knew she shouldn’t, she edged closer towards him until she could feel the line of his body against her side. The truth was, she didn’t know what she and Koschei were exactly. She only knew that _something_ was happening and it was dangerous enough without doing something stupid like letting him move in.

**************

When the Doctor woke up the next morning, Koschei was wrapped around her like a limpet. It was the first time he hadn’t vanished by the time she’d woken up but before she could panic -

“It’s Saturday,” he grumbled, “Stop thinking so loud.”

And then, Koschei’s arm tightened round her waist. It was a surprisingly comfortable way to wake up and before she could wonder whether or not it was wise for him to stay any longer, she was drifting back into sleep...

The second time she woke up, Koschei was gone and her heart did a confusing, devastated flip-flop until she caught the sound of water running from the bathroom. When he returned, his hair was brushed, his face was washed and he was fully dressed.

“You’re awake,” he said, bending over the bed to drop a kiss on her cheek, “I’m going to get my stuff.”

The Doctor only blinked up at him dumbly, her brain still foggy with sleep. She wasn’t used to seeing him first thing in the morning but it seemed that he was already leaving. It was only when she was halfway through brushing her teeth that she remembered with a cold horror _why_ he was getting his stuff.

By the time she’d showered and dressed, Koschei was back. His idea of moving in seemed to consist only of bringing his toothbrush, an eyeliner pencil and a massive pile of books that he borrowed from the Matrix. It was a discreet enough collection of belongings that the Doctor’s panic immediately eased.

Besides, he’d also brought two portions of scrambled chilgreen eggs from the refectory and she wasn’t one to turn away breakfast - not when Koschei was also holding a box of sweets. She was only halfway through the carrot fudge when she made up her mind. He could stay for the weekend, but he’d have to go back to his own room on Sunday evening.

Not that he’d been waiting for her permission. Koschei had practically inhaled his breakfast and seemed to have settled in for the day. Spread out around him, taking up most of the dining table, were his library books and a variety of highlighters in different shades of purple.

“‘Power, Politics and Punishment,’” the Doctor read aloud from the spine of the dusty tome Koschei was pouring over, “That’s... erm, why are you reading that?”

She hoped she didn’t sound too suspicious, but it was hard not to be when it came to Koschei.

“It’s fascinating,” he said, before he shoved a pile of books towards of her, “Look, these are ones I’ve read already.”

She scanned their covers quickly. ‘The Founding Fathers’, ‘The Council, the Division and Gallifrey’, ‘The Early Years of the House of Rassilon’. They all sounded incredibly dull but Koschei _was_ the heir to the House of Oakdown and there’d be a seat on the High Council for him one day in the distant future.

“I didn’t realise you were so interested in politics,” she said.

“I’m not,” he said, “I was wandering around the Matrix and found these. Their bio-locks are rubbish. Did you know that the first Lord Rassilon was utterly ruthless?”

The Doctor blinked and, ignoring the implication that he’d hacked into a locked room and taken books he shouldn’t have access too, replied carefully, “No, but I s’pose that makes sense.”

The House of Rassilon had held the Presidential seat since Gallifrey’s founding. It was fair to assume that an unelected line of leaders would have gained their power by doing something ‘utterly ruthless’.

“It’s fascinating,” Koschei said, “What they did to take power.”

“They?” the Doctor asked.

“Lord Rassilon and Lady Tecteun. They had an unquenchable thirst for power and-" Koschei rambled on, his voice ringing with admiration, but the Doctor was barely listening.

She’d already been worried that Koschei hadn’t been motivated by the right reasons when he’d held back from hurting Mr Pink, and it was moments like this that she remembered he was only seventeen and _particularly_ liable to bad influences. His morals were already questionable; he didn’t need to spend so much time reading about dictators and power-grabs, even if it was technically educational. There were far better ways to spend his time.

“I had an idea,” she interrupted swiftly, “Something we could do together. Something more interesting than this.”

Koschei immediately stopped talking and his eyes widened like huge, expectant moons.

“If you want, I could give you my books from the Academy,” the Doctor said, “The ones from my Cosmic Science degree.”

“Are you offering to tutor me?” Koschei asked excitedly, but thankfully, before she could say no - after all, the point was for him to keep himself occupied with things that weren’t bad for him, and that included _her_ \- he continued, “No, I’ll read them myself. It’s only rocket science.”

The Doctor rolled her eyes. He was annoyingly arrogant but he was probably right.

“I’m not going to tutor you,” she said firmly, “But we can discuss the topics if you want.”

“Can I have your research notes too?” he said, “I’ve already read all the papers you published. Did you write anything that didn’t make it?”

“You’ve read what?” she echoed and to her surprise, Koschei suddenly looked awkward.

“I told you,” he mumbled, “I looked you up. After the Archangel Network.”

“You read my work,” she said slowly, “And you understood it?”

It was Koschei’s turn to roll his eyes and then he said something that made her blood run cold.

“I _really_ liked your PhD project,” he said, “‘The Oncoming Storm’ was... impressive.”

“I wiped out an entire animal species,” she said, blinking at him in confusion. He couldn’t have meant the event that had nearly derailed her university career.

“I know,” Koschei was grinning now.

“There isn’t a single dalek left on the planet,” the Doctor frowned at him.

Koschei only nodded, “What was it like? An entire species burning. How did that feel?”

“I was the only one who could end it,” she said numbly, “They were invading every habitat in Gallifrey. Everything would have died. All the plants, all the crops, all the animals. And I tried. I did. I tried everything.”

“You must have felt like a God,” Koschei whispered, gazing her at reverently.

His awe confused her. She’d made a difficult decision that had saved the entire biodiversity of Gallifrey, if not the planet and yet, her actions had left her peers in the academic sphere wary. It was why she’d eventually decided to go into teaching instead. Teenagers didn’t look at her and see her darkest hour. Except for Koschei, who seemed disturbingly impressed.

“I accept,” he said grandly, as if the Doctor hadn't been staring at him in silence.

“What?” She blinked.

“I accept the offer of your books,” he said, “And all the notes you took and any papers you wrote yourself. I want those too.”

And at the sight of his eager smile, a sudden wave of relief hit her. He’d accepted. He’d stop reading his awful history books, they could talk about space and stars and maybe he’d grow out of this strange obsession with chaos and destruction.

“I’ll have to drive to the Lungbarrow estate,” she mused out loud, “If I go today, I can come back tomorrow.”

“Are you asking me out on a date?” Koschei sat bolt upright.

That wasn’t at all what she’d meant and the Doctor would’ve said so _immediately_ , only Koschei was already beaming at her so brightly that it made her heart thud even faster. And after his ready agreement, she didn’t want to say no.

“Does staying in a dusty house count as a date?” she said, weakly.

Koschei nodded, “Definitely.”

And against her better judgement, she nodded back. At the very least, they could use the time to talk about why he couldn’t move in. There had to be a line and living together was definitely it.

**Notes for the Chapter:**

> Will the Doctor be able to stop Koschei moving in? 🤔
> 
> It’s a bit of a filler chapter I suppose but I hope you liked it anyway!
> 
> (and I don't know what kind of science this version of the Doctor does. Clearly, it's EVERY POSSIBLE SCIENCE)


End file.
